I will lay this out again.
Neither side is going to believe the other side. No agreement is possible between the governments.
The most likely evolution is a military coup in Ukraine, removing the government and murdering all the CIA and MI6 people. Simply that. The replacement will be military technocrats.
The reason this is more likely for Ukraine than Russia is the intelligence directorates are configured differently in Ukraine from Russia. The Ukraine intelligence directorate reports to the military. They have no way to independently detect a coup unfolding.
The Russians security directorates are external to the military. They could see such a thing coming. And there is that tricky matter of Medvedev being Putin’s heir apparent, and he’s far more hardcore than Putin.
And that’s that. There can be no agreed resolution. There must be total defeat.