They could be good idea.
Ukraine can trust China they try to protect them if agreed to. They doesn't have to do this with military force and even if Putin suddenly decide that Chinese can't be trusted anymore - China is ALSO nuclear state so direct military conflict is unlikely.
Russia can trust China that if Ukraine and China agreed that Ukraine will not enter NATO(one of reasons for this conflict according to Russian side) - China will honor this too.
(It's unlikely Russia will trust NATO on this anymore).
Issues of Crimea and Donbass and Donbass remains but Donbass is easily solvable - just let China control implementation of Minsk agreements. Crimea is more complex .