ok so seeing how this idea hasnt taken off the way i hoped it could, i threw together this screenshot to try to show what the interface would be like. and yes that is just a slight edited picture of swirlymms.
by selecting the person from your contacts or putting in a ten digit number, and then specifying the carrier, the app would automatically set up the "to" via the workaround i posted above.
ok so the positves of this app
1. it could include texting sideways if wanted
2. mms via the email app
3. no cost, plus u can send messages when u only have wifi, no cellular data
negatives
-u would need to know the carrier of the person ur trying to message.