And who is going to hemm in the hostile Fifth Reich EU? If you wish to speak of balances of power, then an equally sized EU and RF is balance. Giving everything to the EU and Soros is stupid. With Ukraine and Belaruss, Russia will be hobbled and eventually absorbed into the EU Super State, then what do you think will happen to the US position in the world? Most Americans don't seem to think this one through. They knee jerk against Russians and for the Germans and French from past realities, but those don't exist any more.
I think these things through. I've lived and worked in Moscow, Kiev, that hideous Soviet-throwback wasteland Minsk, and Brussels - my least favorite city in the world.
Since I reject your premise that the EU is even in need of 'hemming in' anytime soon, there's no real point in answering your question. The best way to hem Europe in these days is to not try to get them to do anything, and they'll just cloister themselves in their little fantasy world for as long as they can maintain the delusion.
Aside from that, playing them one against the other is all we need to keep them on the sidelines, which is why that's exactly what we do anytime there's a serious clash of interests. Ukraine adding weight to Poland, Hungary, the Czech Republic and so on would be the most effective check on the Franco-German core than anything else.