I think it's a cool idea, and would fill a niche. Understand, I wouldn't trade my Axe FX II for one, but I think there's a large number of people who wouldn't spring for a II but would for an effects-only version, because they love their amps, but want a multi-effector that does a lot without compromising sound quality.
A couple of years ago, I had a Budda Superdrive 30 that I loved the sound of, and I strongly considered getting the TC Electronics G-system just for that reason (finally gave up on the Budda because it kept breaking down).
And when you think about it, most working guitarists are already familiar with the concept of having an amp that does two or three levels of clean-to-distorted, and then augmenting that sound with pedals to get their effects. I understand the allure of pedals; I sold quite a few of them when I bought my Fractal, but I think most big-time pros use pedals rather than multi-effectors because the quality isn't comprised in favor of quantity. For a long time, I used a Digitech rp500, which was kind of like one of those Chinese Buffet places--lots of different stuff that kind of tastes the same. I only used it because it had a global amp-modeling disengage button (to use effects only), and a "pedalboard" mode, which--like the Axe and the MFC-101--allowed switching between what amounted to multiple combinations of different individual pedals.
Besides, I've read a few interviews of big-time pros--including Fractal endorsers like Lifeson and Petrucci--who have the Axe II in their setups ONLY to generate effects...