Underused 1000-1900 PODs

  Again it depends on what butterflies occur to prevent his rise to power?  The republic was in a mess by the time he seized control so if not him some other military strong man probably would have taken power.  An alternative might not have been as great a general as Napoleon was in his prime so the resultant empire might not have lasted until 1814/15.  On the other hand they might have escaped his hubris and hence established a smaller but lasting French empire.

  Another alternative might be that the republic is crushed very early on, or simply never comes into being.  In which case Napoleon either is a minor artillery officer in the French army or dies in some minor clash and is basically unknown to history.

  Well that's one option that I've seen suggested.  That slavery was actually declining in importance, even in the south, until the gin was invented so if that was delayed for even a couple of decades you might have seen the deep south settled by small farmers rather than large slave plantations and a continued decline in its importance.  Not sure how viable this scenario is however.

  Another possible option is that the US is faced with a clear threat and needs every available resource.  The only at all likely option I could see here would be if Napoleon decided to keep to the Peace of Ameins, hence avoiding war with Britain, doesn't get bogged down in Haiti [or wins quickly there] and decided to keep Louisiana, which he would have grabbed back from Spain.  In which case there is the possibility of a French-US war where the US would be faced with serious problems and if it offered freedom to any slave willing to fight against the French you could possibly see a very large free black population, even in the south and the resultant collapse of the plantation system.

  In a crisis against the world's current No. 1 military power with bases [Louisiana] and a fleet able to both threaten their coastline and bring over and supply substantial army forces I think there would be a widespread acceptance that such a power would be required, albeit probably with a lot of questions post war, depending on how that conflict goes.

  In terms of compensation I think that would be required.  Depending on the state of the union after the war this could become an empty gesture, say if the currency is in the pits and hence former owners being given worthless government script simply because it can't afford anything else.  Or given the imbalance of forces, assuming no one [cough Britain cough] comes to the US's aid or Napoleon isn't distracted by new wars in Europe you could end up with French annexations, especially of the western portions of the US i.e. those just to the east of the Mississippi which could make some of the issue moot.  Albeit that I think there wasn't much white settlement [and hence black slaves] in that region at the time.  We're also got the issue that Florida is still under Spanish control at this point and albeit with some resentment Spain is a French ally.

  If the US does come out of it much better then its in a condition to pay such compensation although it might be a burden on the country and hence a source of resentment by the non slave holding majority.  A lot might depend on how the freed slaves are treated as well.  Could there be attempts to renege on the deal and re-enslave those freed under the agreement?