Putin does not have further conventional escalatory potential in an offensive war: in short, he's 'maxxed out' on the amount of force he can deploy. It's a lot of force, it might grind down Ukraine. But if we say 'no' to his 'deal,' he doesn't have another card to play.
He can rearm over years and invade western Ukraine
That sounds like a strong reason to reject any deal now and instead transfer more arms and munitions to Ukraine in order to maintain the depletion of his force and the stress on his economy and thus prevent full reconstitution.
That is a great plan!