Russia won't stop at 'some' territory, that is the problem.Removal of western support would spell the end for Ukraine. Not saying it's something I necessarily agree with but the west could likely impose a diplomatic solution involving some loss of Ukrainian territory if it could actually avert WW3.
It's not what is fair, but then if it actually came down to Ukraine losing some territory versus nuclear weapons being used then I think I know which was I'd rather it went