Not the OP, but I can answer your questions :)

Posting data in fake keys or hashes cannot be fixed without major changes to the protocol. You would have to disallow any sort of hash output (no more p2pkh, p2wpkh, p2sh, p2wsh - which are all still used!) and enforce that public keys in bare pubkey outputs (p2tr, p2pk) are actually valid. However you can very easily grind public keys to still mostly contain the data you desire, or tweak them by adding something to them, so this doesn't really help either.

As for utreexo, there is work being done in Bitcoin Core to make it easier for utreexo nodes to re-use the Bitcoin Core code for their own implementations. There is a chance that Bitcoin Core will eventually adapt their validation model too. I do think their model is attractive, especially for running nodes on devices with restricted io capability.