Biggest issue there imo is secp256k1. It's just not a curve you can easily do this kind of core infra stuff with. It's not supported by passkeys (webauthn), it's not supported by SubtleCrypto, it's not supported by the secure enclaves of iOS or Android devices, you can't use a secp256k1-based certificate to sign a tls 1.3 handshake, then there's JWTs, JOSE, list goes on. It's just absent from a ton of web standards. mainly because it isn't NIST-stamped, so it's sidelined most places by secp256r1. Basically if the goal from the start is to replace the certificate chain and all the rest, secp256k1 is definitely not what you'd choose.