This sounds like it might be getting close to (but not quite at) Sui’s address owned objects, which they allow to bypass consensus.
Have you studied the Sui model and their implementation?
Would this proposal mean that such “stateless” extensions could ever bypass consensus?
If not it will be worthwhile spending some time documenting the sense in which a (pseudo-?) “stateless” extension still needs validation - if nothing else it will be a bridge for Sui developers moving to Substrate based chains.
Related?: