Not to mention even if China managed to create a peace deal the moment the war ended all of America's attention and efforts in the Ukraine would be transferred to undermining China. If China threatened the Ukraine to accept a deal (no matter how generous) or they will start arming Russia the Ukrainians will run to the Americans and claim the Chinese are bullying them.
There's no chance a peace deal is going to work, both sides are as intent on fighting as the day they started. I don't know Xi is even bothering bringing this up. It's not worth the effort even for political brownie points.
Even if the peace offer isn't acceptable to either side (and I agree with that assessment, both side still have plenty of fight in them), coming forward with a peace plan is an useful gesture to show rest of the world that there's at least one superpower around doing serious work trying to end the war instead of pouring more oil on it.
Once Ukraine publicly rejects the peace offer China will have more leverage to do the "don't blame me, he choose violence" thing and increase aid to Russia. I still don't think you will see entire platforms in Russian hands so no chance of seeing 99A duking it out with Abram, hence why I was thinking what sort of UCAV aid can there be while still maintain plausible deniability.
According to Ayi's friends on Weibo last year there were already cases were groups of PLA vets submitted request to volunteer for Ukraine and fight as PVA, but their requests were predictably shot down.