They could do some exercises together - I think Ukraine is resigned to the loss of Crimea - sensible decision in withdrawing their troops.
They’re divorcing themselves from Crimea but from Russia as well. Like I always like to say, better a good divorce than a bad civil war.
Ukraine is going to defend its territory but has no interest in picking a fight with the Crimeans or provoking a war with Russia.
I’m seeing reports of pogroms in Kievs, Right Sector thugs going door to door and asking what political allegiance people have, throwing people out of flats to give to “heroes”, etc.
If true, and this spreads to the East, Russia will intervene.
Putting NATO forces into Ukraine would be considered a serious provocation by Putin. Obama and his 'Team' are not deep strategic thinkers and this move has to be considered for response and next moves. While this might be a move that would give Putin pause, it could have the opposite effect and put dangerously small US Military assets at risk.