Operation Righteous Sword - AKA, Europe's Desert Storm

Thank you. 
Those security battalions have two objectives; it's a PR stunt, largely to make the more gullible audiences think that the Baltic's Russian population's actually want Putin's tanks rolling down their streets (by and large, they don't, but as in Ukraine there will be a number of volunteers) and secondly to give Putin a force he can wash his hands of when 'dirty' counter-insurgency work needs doing. These battalions will have at least a veneer of deniability. As you say, there won't be enough volunteers to bring the units up to strength. A lot of the members will likely be retired Russian soldiers, mercenaries with the Wagner Group and similar organisations, and possibly recruits from Ukraine. 

As for the security issues and potential for terror/commando raids, I'll answer that with Stevep's question below because my the reasoning for both answers is the same. 






My plan is for the Russians to go with a more deniable means of combatting the build-up, through cyber attacks, terror/Spetsnaz cells, stirring up anti-war dissent in the West, etc. Putin can (at least in his mind, for the purpose of TTL) spin the occupation of the Baltics as a defensive move to prevent a genocide of Russians living there. He thinks he can get away with it in terms of international relations, gambling that NATO is bluffing. Now, Putin is NOT Saddam. He won't sit there and allow the Allies to build-up a massive offensive force in Poland without interfering. But he won't fire the first shots either, not openly at least. In his mind, if NATO does go on the offensive, he can still spin that as Western aggression or imperialism. Occupying the Baltics is at least on the surface a move to protect Russian people everywhere; invading Poland is not. Russian efforts to stop the build-up will come in the form of sabotage, cyber warfare and other non-attributable (at least not officially) methods. 

Now, I am trying to reverse the normal scenario of a NATO defensive operation here, and I'm mirroring the Gulf War and the buildup to that somewhat. Once the air campaign starts, Russia will be moving to secure it's flanks and create some depth, but anything that brazen is off of the table until NATO fires the first shots. 

Excellent work.
Chicksands must have been Spetsnaz and they've just had a bad night!
Great buildup of tension too.
Some of the smaller NATO countries will be ripe for ops like Hamburg to frighten, destabilise and cause distraction.

A journalist might call a ship a warship but that doesn't mean it is one.
The media often call anything tracked a tank even if it is only mounting a machine gun.

Honestly I don't even think it needs a gun to be called a battleship. The hypothetical prisoner, who may or may not exist, could be mighty useful. But to the outside world, he is a write-off. 






There won't be any serious torture or abuse, but he's likely to have a pretty nasty time regardless...if he exists. 

If this Spetsnaz man did exist, ahem, hypothetically, ahem, he would be being held at a secret facility at an RAF base somewhere in East Anglia with the RAF Regiment running security and people from Defence Intelligence, Five, and Six running his interrogations. He won't be being waterboarded or anything like that, but lots of confusing tactics, loud music, flashing lights, etc, could be used to soften him up. 

That is, if he exists. 

There is a whole range of ways that the UK can be hit, just as that general says. The airliner shootdown shows just how that can be done with little military effort too.