I’m not (currently) developing an account contract, but if I would, I don’t think I would be using this. You mention simplifying implementation as the rationale for this standard. IMO it does the opposite.
UDC is just a syscall wrapped in a smart contract - to call deploy_contract, I’d have to have a declared const of its address, a defined @contract_interface and a external call in my account contract which is way more complicated than just calling the deploy syscall.
Besides that, how would this work on an L3? Would the UDC’s address be the same on each new L3 instance? If so, who’s the authority that deploys it?