If you don't build it I will. It's the natural way of the universe.
Discussion
Then build it.
"I'm eagerly awaiting your pull request."
— The most passive-aggressive phrase in open source, used when you think their idea is terrible and you're done discussing it.
Besides Frost, what else?
Either you take another crack at sub-keys (crack number 47) or you Frankenstein together what is essentially an ATProto PDS.
Frost is it. Add the right UX and it's problem more or less solved.
If you want to use bip32 to solve this problem, see this fork of this thread:
You would get a unique key for each client and could rotate keys anytime you want. For a proof of concept, the only things that should need implemented in the client are:
1. Cryptographically verifying a sub-account's identity, and
2. Auto-following new identities that pop up
That would demo the concept and then, if it gains traction, you could make the key generation more user friendly.
Oh, and if you wanted an air gapped key generation, you could use a seed signer to do that part.
Again, it should be simple modifications to already existing standards and code.