The trouble with agreeing with anything with Putin is that he lies, and lies, and lies, and lies. No promises hold.
If you look at his past actions, he has actively and effectively sewn strife and weakened the West and extended Russian influence wherever he can. If there is a negotiated settlement now, it will only hold for as long as he can rebuild, possibly by strengthening links with China. It will take him some years to get back to a position where Russia is stronger, but he -will- try again. If not the Ukraine, something else. The more that he gains now in the Ukraine, the quicker he'll be back, like a rat finding another way into the larder if one hole is stopped up.
The price is very high to the people in the Ukraine - I suspect that the cities will be razed - but I don't think that settling for the first offer on the table will be good for the Ukraine or rest of the world. In fact the more brutal he is now the more likely that people will negotiate a ceasefire, but tactically it might be better to hold out.
China says the relationship with Russia is solid, despite all this, but I should think Xi Jinping might want to be very careful how he deals with this master strife-causer.