Putin and his Oligarch buds are a pestilence on this world but reality eventually will be recognized. If he is given no way out then this thing is either going to lead to a global conflict or at a minimum, the nation of Ukraine laid waste. He shouldn't be rewarded but some compromise that would be painful for BOTH sides might be acceptable.
Let him have the land his troops control as of the signing of a cessation of hostilities, but with the knowledge that the REST OF UKRAINE will become a member state of NATO. That would solve the issue of those who fear he'd take what was offered, wait awhile, then come back for another "bite". Kind of like what the Palestinians have been doing for 70 years...