The prospects of the UN imposing a settlement with US acquiescence is very far-fetched. The UN didn't do so in the Sudan where the charge of on-going genocide had justification. International intervention is an extreme step one that has no support within Congress. As to the second part, well... If Israel came up with a peace plan as prelude to direct negotiations it would not help. The PA has pretty much stated it's demands and they are beyond what the Israeli public will support. The 'right of return' is still the most serious objection. Only an outright rejection has any hope of changing Israeli public opinion.
Israeli PM to Palestinian President Abbas: We must fight terror together (Haaretz)
from the article: Needed: An Israeli peace plan