In any case, I agree with your idea of a p2pool with a smart contract guarantor, I think we're running out of privacy-friendly solutions. The same goes for hashrate renting, I think it would be a good idea to develop a P2P hashrate rental service with a price per share submitted.
I also agree with idea of P2Pool (which is decentralized pool). While i expect it'll never be very popular due to full/prune node requirement and creating many small UTXO, P2Pool on Bitcoin should able to reach few percentage of total hashrate when P2Pool for Monero could have ~4.8% total hashrate.
[1]
https://p2pool.observer/