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". Wink And wish that we lived in those times and could make difference.
Past mistakes must not be repeated and thus it of course has to be avoided that a member of this block becomes imperialistic and oppresses other members. All nations shoud be representated equally, so your idea of rotating presidency has my support. Without chauvinism of szlachta and with equal representation of Ukrainians Polish-Lithuanian-Ruthenian Commonwealth could have been a good thing for all involved and a lot of bad blood could have been avoided. But things turned out as they turned out and now we can only focus on not repeating our faults and make the best out of our present-day situation.