LinuxCNC/EMC requires a parallel port, PCI or ISA bus for interfacing to the physical world, so that would need to be worked out.
Porting a real time kernel and device drivers to work with the RPi may be pretty significant, never looked deep enough into the code to have a estimate, but it could be a lot of work.
Post the question to the LInxCNC forum and see what responses you get back, Those folks could bring some solid comments to this thread.
Question, you referenced the reprap/maker/High school projects as one driver for this project, why do you think those existing solutions are inadequate?