I still don't see what mastercoin is doing about this ....
Mastercoin needs more than 80bytes in OP_RETURN for asset issuance. Theirs seems to be a different problem.
On the other hand, a regular mastercoin send only takes about 30-35 bytes. Maybe Counterparty could consider selectively sending common, small transactions with OP_RETURN, and using multi-sig only for relatively unusual transaction types?
I'm fine with this, of course, but it doesn't really address the issue at hand. We'd still need multi-sig for some things.