Not to go too far off the rails, but would it make sense to use a vapor chamber instead of a copper block in water cooling arrangements? I'm not sure the additional cost would justify the performance or not
It would have to be in addition to a copper block (or you'd just have water spraying around the inside of the case).
The main utility of a vapour chamber is to take a heat source that is concentrated in one spot and spread it over a larger contact area. Waterblocks do not really have this problem (you can design a high-flow block that moves all of your coolant over just the surface over the die itself) so adding one is unlikely to produce any improvement in performance.