The obvious downside is that the cost for all those multiple certs. The market would triple or quadruple overnight. CAs might just love this idea to death, for

The obvious downside is that the cost for all those multiple certs. The market would triple or quadruple overnight. CAs might just love this idea to death, for those reasons. All hobbyists and small shops will be out of luck however (and there are a lot of those), they have to go back to sending plain text in the clear.