Speaking of potential states and alliances, what would you think of forming an alliance of Baltic and Slavic states, including Czech Republic, Slovakia, Poland, Ukraine, Belarus, Lithuania, Latvia and Estonia? Of course not all mashed into a single state, more something like an alliance based on economic and military cooperation.
Ah, so you like Piłsudski's "Międzymorze" idea then?
Some such ideas already exist regarding military:
Or are planning to be expanded:
Though I don't know if there is such economic cooperation yet (aside from EU and Eastern Partnership idea of course).
EDIT – I see now you asked what my opinion is on it. I think it is good entry level federation, though eventually I would like such thing between all European states (not like in current form with EU, but something similar minus multikulti, American influence and mass immigration of muds from outside Europe).
There should be rotating presidency between them also. Actually, Polish-Lithuanian Commonwealth (minus Czechia and Slovakia) was already existing version of what you were saying, but I think it should have been called Polish-Lithuanian-Ruthenian Commonwealth. Problem was that Polish szlachta was shamefully arrogant and narrow-minded towards your people and this caused Chmielnicki Uprising, which could have been avoided if your people were considered equal in this Commonwealth by szlachta.
History would have looked different then, because as equals, we would have been too strong for anyone.
But unfortunately, all we can do is "gdybanie". And wish that we lived in those times and could make difference.