Im using bip32 already, because one of the proofs that you can present in a catastrophe case is reveal your xpub to prove that the different subkeys what you have used belongs to the same xpub. I called derivation tree proof. Afaik with bip85 you can do the same in some way since it use bip32, but doesn't have sense for this use case. But maybe you have an idea? 👀