Have you thought of using an android based embedded platform to run GCodePrintr on the hardware that is controlling the printer itself?
I have been wanting to get a UDOO quad core + ramps-fd and a cheap LCD from http://chal-elec.com (if they ever restock). With that combo everything would be completely integrated. This would open the doors to have intimate control over the hardware that may be a bottleneck in the future for you.
Just a thought…