An imposed solution will make demands of BOTH sides. Those demands will be enforced. Both sides are looking at undesirable terms if they are unable to reach a negotiated peace. For instance, Palestinians are likely to lose the right of return -and also just financial compensation for giving up that right in negotiations. Likewise Israel will lose almost all settlements that are not on or adjacent to the Green Line. Israel could also lose significant US support if it forces the USA to abandon it's attempt to bring about a negotiated peace.
from the article: Abbas urges UN: Bring final end to vicious Israeli settlement campaign