I fully agree, with the caveat that no Ukrainian politician can say that out loud going into negotiations, obviously. However, there will be some negotiating space that will probably lead to some outcome, I think, in which Russian troops will remain on part of Ukraine's territory.
I think a good analogy here is the Welles Declaration. Throughout the Cold War, the United States never recognized the incorporation of Lithuania, Latvia and Estonia into the Soviet Union. That may seem as a weak or diplomatic response to a military occupation, but it had legal consequences when the Soviet Union collapsed, in that it was a resumption of diplomatic relations with those three countries and not their establishment, as it was with all the other Soviet republics except Russia. Therefore, something analogous to that, in terms of Russian occupation of Ukraine, I think, is what would be advisable.