I think that way to solve BGPs security problems might be to use a new cryptographic hammer, "Proof-Carraying Data", where messages come with cryptographic proofs that they were produced correctly. This allows you to basically just run BGP, but every AS proves that it ran it correctly. The proofs take constant time to verify, regardless of how large the network is, or how many hops the routing message has taken. Feasibility is helped by latency not being super critical in BGP and BGP being a pretty simple protocol; which makes computing these proofs plausible.

https://rot256.dev/post/bgp-pcd/

Proof-carrying data has come a long way in the last 10 years.

EDIT: you would still need RPKI, but not BGPSec