Ah, sorry, huge miscommunication and misunderstanding on my part. I've actually been agreeing with you all along.
A large part of the problem is that I've been thinking about my proposal as two separate parts: one part deals with backwards compat with Arc, and the other part describes a hyper-static system for Arc.
When I was talking about "defs", I was talking about the hyper-static part. But you were talking about the backwards compat part. Hilarity (?) ensues.
