I fully support getting rid of the two party system, but at this point in time it’s a fantasy. Maybe next election when Trump isn’t going to be the consequences is where Jill Stein can get her votes.
Unfortunately the Republicans may find someone even worse than trump next time.
I would say an absolutist would be justified in crossing the border if they offer that land back at the end of hostilities in exchange for other concessions.
Even if Ukraine doesn’t reclaim all of their land they could offer Russia kursk for some other equal amount of Ukrainian land in any peace talks.
Otherwise if Russia refuses Ukraine is justified in keeping that land.