This would work except you lose the ability to fall back to a text message. The way that iMessage is set up, if someone sends and iMessage to your phone and it

This would work except you lose the ability to fall back to a text message. The way that iMessage is set up, if someone sends and iMessage to your phone and it doesn't get delivered for some reason, say you don't have data coverage where you are, then the Messages app will try to send a text message instead. If you have the same scenario where you are messaging an email address, there is no such fall back.