Best time for Germany of Hitler's death

Success of the 20th July coup attempt really seems too late, too little for the purpose of this scenario: at least half the body count of the Holocaust has already happened, Germany already suffered substantial wartime losses and damage to its cities, and its military situation has already deteriorated enough that it is questionable it may leverage the Allies into granting the kind of peace deal (1938 borders, no Soviet occupation zone and hence no political division, with or without Western military occupation) that would be acceptable here. It is theretically possible, but it likely requires additional PoDs to change the Allies' stance. Besides, the 20th July case is only the most famous example, but the list of assassination attempts on Hitler includes about a dozen documented events between 1930 and early 1943. There is plenty of more suitable options.

Delay Chamberlain's acceptance of German demands by a few days. Hitler loses patience and gives the order to invade Czechoslovakia. The anti-Nazi coup triggers at his order for mobilization and succeeds. After the junta has stabilized its rule, it eventually renews its requests for the Sudetenland and Danzig in a more tactful and moderate manner (i.e. a request for a plebiscite in both territories under international supervision, with guarantees for demilitarization of the Sudetenland and free passage in Danzig for Poland's trade). Britain accepts them because it remains eager to use a strong Germany as an anti-Bolshevik bulwark and it has no appetite for a general war to preserve Czechoslovakia's and Poland's territorial integrity against a 'sane' Germany.

Since Ludwig Beck was a major member of the German resistance between 1938 and 1944, designated to become President in the 20th July plot, and even more influential in 1938 than in 1944 (he had been head of General Staff till a few months before) he is my best bet for the new head of state of Germany. As it concerns the SS, I assume they would be neutralized without too much hassle; during the 20th July event, when it seemed Hitler had died and the coup would work for a while, several SS units surrendered to the Valkyrie forces without much of a struggle, and the SS were much more powerful in 1944 than in 1938. The members of the SS and the Gestapo that seem sufficiently reliable politically and more professional operatives than Nazi true believers or useless thugs may be recycled in the conventional army or police, the others shall be disarmed and dismissed from service, or purged if they look too dangerous. The SA had been gutted and radically lost importance after the Night of Long Knives, the Kristallnacht was their swan song and they lost pretty much all significance soon thereafter, so I assume they would follow the fate of the SS - also because they failed to stage any effective resistance to the 1934 purge. In all likelihood, the Nazi regime would fall to a military coup just as thoroughly and easily as its Italian counterpart in July 25, 1943.

Nitpick: let's keep our PoDs simple. If you deem best for Hitler to die during a failed coup attempt, no need to invent an ATL one. Let him get a bullet in the 1923 one. Otherwise, I'm actually fine with letting Hitler die pre-1933, as long as this means Weimar democracy stabilizes as a result and gets empowered to throw out the most unreasonable and unsustainable provisions of Versailles treaty (excessive reparations, unilateral disarmament, limited control of Rhineland, prohibition of democratic Anschluss). Which admittedly in all likelihood was going to happen in the 1930s under pretty much any German regime. So I'm entirely fine with the scenario you describe, give or take a few details.

On the other hand, I'm also rather fond of a PoD bringing down the Nazi regime sometime between the Munich Agreement and the Molotov-Ribbentrop Pact. By 1938-39 the Nazi regime had done frankly negligible damage to Germany and the world, and accomplished some good by undoing Versailles, housecleaning of people just as terrible as themselves (the KPD, the rogue SA), starting economic recovery, and wiping out the unbalanced-federalism flawed legacy of unification. If the Oster conspiracy or Maurice Bavaud getting lucky and unleashing a succession struggle that brings the generals in charge causes German democracy to be restored in a few years after a transitional junta regime, the long-term outcome is basically going to be indistinguishable from what you described.  

Well, I agree a Weimar Germany that achieves political stabilization in all likelihood is going to undo Versailles pretty much the same way Nazi Germany did if with much more diplomatic tact and much less financially-reckless rearmament. After all, non-Nazi Germany does not really need or want a strategic window to conquer Europe, any German leader but Hitler, Himmler, or a Communist stooge of Stalin would basically be content with military parity with the Entente and the USSR, a sphere of influence in Central and Eastern Europe, the Anschluss, and ability to force the Czechoslovaks and the Poles to give up their ill-gotten gains. Non-Nazi Germany can achieve such a much more reasonable foreign-policy agenda with a rather more sustainable rearmament pace. Apart from this, the 1920s were a period when the great powers at large did not make much in terms of rearmament, there was still too much WWI surplus lying around, so disarmament did made much of positive financial difference for the Germans. Nonetheless, the extreme, unilateral disarmament Versailles inflicted on Germany was quite unsafe and unfair for Germany. Much the same way, the whole problem with demilitarization of the Rhineland was its unilateral nature. History from 1500 to 1923 shows the Germans had reason to fear an French invasion as much as the French feared a German invasion, so any demilitarization of the Franco-German border, if it exists at all, ought to be bilateral and balanced in the Rhineland and Alsace-Lorraine.

Of course I agree stabilization of Weimar Germany would be near-optimal in these terms. It is just I do not notice that much overwhelming of a difference between that and the Nazi regime being replaced by a DNVP or military regime from the beginning or after a half-decade of rule. Any other right-wing German leader but Hitler or Himmler is almost surely going to make oneself content with what Germany had achieved by the Munich Agreements, plus Danzig, some kind of deal about the Corridor, and a sphere of influence in Eastern Europe, which was relatively easy to set up since the alternative was Stalinism. Czechoslovakia had turned itself in a client of Germany after Munich, anyone but Hitler is going to call it a satisfying outcome. Other right-wing German leaders had no urge to start a continental war of domination, at most they would start a war with Poland after diplomatically isolating it (not so difficult if Germany honors the Munich Agreement) if the Poles prove unreasonable. Even so, the likely outcome is Germany recovers the 1914 border and Russia seizes the Curzon line border, something Europe can entirely live with. They won't do anything more radical barring extreme developments such as a civil war in France, Italy, or Russia.

No doubt the loss of the Jewish elites was a significant one for Germany and it is going to sting even if Nazi rule is limited to a half-decade or so. If it is gets replaced by DNVP or military rule from the beginning, such loss is not going to happen, since non-Nazi right-wingers would at most give the Jews some propaganda badmouthing and try to limit their influence on public life; this is hardly going to be a serious problem for Jewish scientists, bankers, or other non-political elites. I'm oblivious of any other significant 'best citizens' loss Germany suffered among non-Jew political opponents or victims of Nazism, apart form a couple cases such as Thomas Mann and Marlene Dietrich. Most of them apart from the far-left fringe are never going to leave or shall most likely come back if the Nazis never come to power or are deposed before WWII. The far-left fringe was mostly a bunch of Communist thugs that were as bad as the Nazis in their own way or would-be spies and traitors, good riddance to them. The Nazi education policies were indeed moronic but if they are replaced by a more sensible leadership within a half-decade at most they shall hardly do any serious damage.

The Weimar political system was quite fine on paper but had grown so dysfunctional by the 1930s I'm not sure there would be that much of a long-term difference if WWII does not occur and homegrown political developments restore democracy in Germany after a decade or so without giving foreign enemies another opportunity to screw up the German people. I'm skeptical the Nazis did truly that much to destabilize Europe before 1940. History shows the dysfunctional spawn of Versailles such as Czechoslovakia and Yugoslavia had their domestic flaws as much as external factors to blame for their repeated downfall. The foreign policy of the Second Polish Republic was one of the biggest slow-motion suicides of the last century, an invitation in glowing letters for another partition to happen. The only thing deserving sympathy in its demise was it left the Polish people at the mercy of two of the biggest mass murderers in history.

Absolutely yes, its leaders signed Versailles under duress hating it themselves and knowing it would make them reviled in the eyes of the German people, and tried their best to undermine it before its ink was dry on paper. When the Entente stops being willing or able to enforce it, they shall restore conscription, expand the army to full size, and cast aside arms limitations about tanks, planes, and stuff. Their objectives shall be a democratic Anschluss, military parity with France and the USSR, enough military power to force the Czechoslovaks and the Poles to make a favorable deal about the Sudetenland and the Corridor, and the hard power means to support an anti-Soviet sphere of influence in Eastern Europe. However they are not going to mind some kind of mutual arms-limitation treaty with the French that does not emperil Germany on its Eastern border. They would want demilitarization of the Rhineland gone as an unilateral measure but would not mind its consolidation as a bilateral measure extended to Alsace-Lorraine, nor creating an analogue in Tyrol with Italy once the Anschluss happens. They are not going to care much about naval rearmament, the Anglo-German Naval Treaty would in all likelihood be more than satisfactory to them.