It seems to me that the 50 1.2 (I have one and love it) would fail both of your criteria... I am sure that there are other lenses that would fit those criteria better.
The 50 1.2 does not sell in a lot of copies and I couldn't see a new one having massively better IQ, which is its most important characteristic.
And I would not buy a new hypothetical 50 1.2 that would achieve smaller size / lighter weight by compromising with optical design with digital corrections.
Generally speaking, my humble opinion is that there are a number of gaps in the RF lineup to fill before Canon should start looking at mkII versions. Especially not for lenses without glaring issues.
So far they have updated only the 70-200 2.8, but even then the 2 lenses are sufficiently different that you wouldn't call the Z a mkII of the original.
Both the 50mm and the 85mm f/1,2 are optically superb lenses. Neither I believe they could be dramatically "improved" to justify a version "II".
Lighter and smaller doesn't suffice, in my opinion.
There are indeed still too many gaps in the RF lineup that could/should be addressed first, like a longer macro, TS-Es, new big whites, 28mm f/1,4, 35mm f/1,2 or, why not, f/1,0 and so on.
Mk. IIs are nice, but filling holes is even nicer!
My 2 centimes d'Euro...
