You're asking for a different form factor, whether you admit it or not. Sticking a touchscreen on a clamshell notebook is a gimmick, nothing more.
I don't dispute a touchscreen would be useful in your profession, but I can tell you that you won't be drawing for long on a clamshell Macbook Pro with a touchscreen.
It certainly wouldn't be a gimmick, it would speed up my workflow massively. Right now I'm using a insanely powerful PC for work and my MacBook Pro is sat next to me waiting to be used. If I want to draw on the screen I get my Cintiq out as I don't like storyboarding or designing characters on an Intuos Pro. That saves me a hell of a lot of time and I can use all the same apps I use on my PC, not crappy mobile versions. The ability to pick it up and draw instantly on it would be a game changer. That's why my next computer will be a Surfacebook.