I’ve been thinking about ways to take advantage of multiple asymmetric encryption schemes so that each key could be a backup to the others in case of cryptanalysis of one given scheme.
Those public key schemes could each secure one share of a symmetric key splitting scheme (as answered in Is there a multiple asymmetric encryption algorithm, which requires all private keys to reveal the secret?).
Something similar could also apply to digital signatures (just requiring all signatures to be valid) or key sharing schemes (just inputting multiple shared secrets into one KDF).
Is there precedent for that?