Ukraine's position seems to be quite simple: go home rus nazi invaders and let there be peace.
Your Putin clearly doesn't want to accept that. So what do you think should be a “proper” negotiation proposal ?
Not for me to say.
Each side has an ideal desire and something they are willing to accept.
Negotiation is coming to an agreement.
It doesn’t occur until both sides want peace - or one side defeats the other and imposes what it wants.
There is a cost to both options.