If Ukraine ceded the occupied territories Russia would just launch a new offensive. Russia wants a territorial dispute because they know that will keep Ukraine out of NATO.
As noted several times. Hell, as SFLUFAN further points out, that's also having to trust that the alliance could even all agree to Ukraine's entry in the first place, nevermind the subsequent likelihood that there's never a chance to actually discuss such from repeated Russian incursion - which itself could end up a factor against such a proposal.
It's just so contingent on a bunch of 'ideal' probabilities after that first bitter pill that you'd be hard pressed to convince anyone of it, even if the option is technically there. While on the flip side, there's not really a lot else to be given that would even seem to nominally satisfy Russia's interests that NATO or Ukraine are in a position to really give. It's hard to see what solution they can really bring together