I had originally planned for the gantry style because a glass and aluminium heated bed would be heavy to move, but I think that with enough gearing it could be used in just the y axis. I think my new plan with have the bed moving in Y, the extruder in X, and the extruder/x axis rail moving in Z. My other end goal (I know my goals seem excessive), is to make the upright frame part (x axis and z axis) tilt 45 degrees to print on an infinite belt setup. I know that this likely has zero practical purpose other than being cool, but If I have the opportunity to have a 750mm x 750mm x infinite printer, why not?
To put that size into perspective, I could print a full size kayak for under $60USD in ABS pellets. Obviously it would be stronger if it was made in a different method, but for prototyping, something like this could be very viable. I can't imagine that there are too many people offering 3d printing services on one of the many print ordering websites that could print something that large.