IMO this is neither needed nor desirable. ("Neither use nor ornament" as me granny used say.)
It clearly isn't needed since there are IMO already sufficient degrees of freedom in the AC profile, i.e. whatever their problems, DNs are cheap (certainly relative to paying all those policy-gank consultants and lawyers!).
The reason it isn't desirable is that AC usage is still almost non-existent, and adding yet more complexity is a very good way to ensure that things stay as they are.
Stephen.
PS: I could try start a separate disussion about PKIX feature-creep, but I won't. (Oops, maybe I just did:-)