Actually i've thought of this idea when i was thinking of forming my band in the past. Its cool cause u can have lots of effects and its so much more versatile..U can play almost any genre..new age, funk, neo classic, techno, anything...
But the main problem i realised was how it would look on the stage...
Guitarists are more mobile..and can interact with the crowd..unlike us keyboardists..lol.. Imagine a whole concert with 2 keyboardists shaking their bodies non stop in that same location... Think about it..lol..it looks quite funny actually..