No, I don't want to reconstruct the key, I just want these providers to construct signatures, which apparently FROST can do safely -- I don't get why you can't do that with MuSig2 (wait, I guess it just doesn't work because MuSig2 has the "distributed key generation" step built in).

So I, as a user, don't have to do any cryptography or hold any keys during my daily life as a Nostr user, I can just instruct clients to fetch signatures from a server somewhere, and that server will coordinate with the 3 entities that hold my key shards to get a signature, then return the signature to the clients and, boom, I have a signed event.