Unless I misunderstood, you're trying to guage community reaction here? If that's the case, here are my thoughts, for what they're worth:

• I like your register( bless ... ) idea better. It's not a whole lot more to do, still takes care of a lot of drudgery, but doesn't make me quite so nervous. I don't like overriding builtin functions in general, much less one like bless.
• Perhaps you could use the Class::InsideOut:: prefix instead of just InsideOut::. Perhaps it's a little too long, I'm not sure, but it seems a bit more descriptive.
• The refaddr to id alias doesn't bother me all that much, as long as it's done in standard ways. It's certainly less to type. :-)

Closing, I just want to point out I don't feel very strongly about these opinions. They're just my gut reactions. If you wanted a more thorough discussion... well, maybe someone else will post that. :-)