Well I got the book and I'm pretty impressed so far. I like that you can not only translate your MWD characters into Total Warfare rules, you get a whole subsystem for making TW characters such as you find on the little mech cards, with gunnery/pilot ratings and special pilot abilities. I like those SPAs and it seems like you could either do a freeform campaign using mainly TW rules (and just playing very rules light outside of the mechs), or create a hybrid game that uses MWD outside the mechs and TW on the battlefield.
Obviously I might revise my opinion when I get a chance to try it, but so far this looks to be exactly what I was hoping for.