So... how many records and zones? I'm pretty sure I could convey it if I could work out what you were talking about.

You went from "you can't even comprehend or convey the massive number of records and zones that are involved" to one v4 /24, managed "at scale" but by an ordinary consumer, who you expect to be capable of programming. This is a bit all over the place.

It's not any harder to deal with v6 reverse DNS than it is v4. In fact, making every reverse label 4 bits instead of 8, combined with v6 being much bigger than v4, makes rDNS much easier to deal with in v6 because you can generally delegate reverse zones on exactly the same boundaries that you delegate the corresponding IP blocks. In v4, you often need to delegate on boundaries that aren't /8, /16 and /24 and it suddenly gets more annoying.

Scaling up for rDNS is no different to scaling up for forward DNS. It's a well-understood problem.