PQ cryptography has all kinds of wild key sizes and signature sizes, some very large.

For Mosaic I've been ruminating about multiple algorithms (in support of nostr backwards compatibility) and from that considering not storing keys or signatures in the records themselves, but rather just hashes of these. Then you look up the keys and the signature by their hash on a keyserver (also serving signatures). Self-hosters would run their own keyserver. Separating large keys saves data by not repeating them, but separating large signatures does not since every record has to have a distinct signature... but in PQ cryptography it is usually the signatures that are wildly large. So it unfortunately doesn't quite fit my idea.