wow harmony - that's the clearest i think anyone could have put into words all the different variables going on here - good work
but if you want a piano - play a piano - the problems with a guitar controller are 1st, the piano is going to sound like it was played on a guitar (not like two handed parts with 5 notes finger patterns and such) - and 2nd, it's not as natural as you think to play midi guitar - every little extra sound is recorded - you have to play it in such a precise manner that you lose the whole feel of playing your guitar how you naturally do so