It is not required that Ukraine become Russia as it was a part of the USSR.
I don’t think total control is necessary. Hegemonic status for Ukraine will likely be OK. Of course I really don’t know.
I think that NATO on the border, EU hegemony, is for Russia very undesirable to the point of not letting it happen.
If you look back a few years, the whole notion of the Iron Curtain was to provide a crush zone, a place to defeat invaders, before they could set foot on the Motherland. That concept is for a number of reasons reduced to Ukraine alone
You’re being awfully generous with your planning for Ukraine and its nation by not forcing it to be part of Putin’s Russia. But Ukraine’s freedom is no threat to Putin; it’s an excuse, but it’s not a threat.