Come to think of it, Delta seems to have come up with a good model for MRTC. The model is called "Song". I won't say Song was first with this model, maybe Jet Blue was.

If you go to seatguru.com and compare the Delta regular 757 plane with the Song 757 plane you find that there are more seats in the Song plane as well.

On the Delta forum someone ranted about the amenities that Song has that those who need to fly "mainline Delta" won't get. It is too early to say whether the Song business model will succeed but give it a reasonable trial period like two years and maybe mainline Delta will gradually acquire MRTC like Song too.

Travel tips:
http://members.aol.com/ajaynejr/travel.htm