A lot of being discussed here last few days, hard to comment on all specific details through here, but here's my view:

• Cache per RegionAccess IMO is just fine. From what I understand, this seems to make it easiest to use the most efficient cache keys that do not contain entity/collection names, right?

• As Radim said, some functionality might not be fully possible with cache per region access, e.g. max entries for a entire region when this region is shared between different caches... Not being able to do this seems fine to me, not sure this is such a popular option.