Its a rather "long road" to write a Grbl replacement (perhaps later), but converting gCode from XYZ to UVZ is not. I have seen that someone has already done this on the Internet (sorry I have lost the link). So basically after conversion you can use Grbl instead.
Perhaps I am wrong but Grbl does not appear to handle UVZ coordinate systems.
I already have a gCode Filter project that can be co-opted into service.
After filtering the gCode to remove "redundant" segments (i.e. the main function of gCode Filter), I only need map the UVZ space and to insert the critical points.
I have made a start, set up two graphical results windows, one for XY space and the other for UV space. Still about a days coding left to complete (wishful thinking perhaps?).
One of the issues for construction of a SCARA is the bearing. Nearly all the projects I have looked at are DIY. It would be nice to get something reasonalbe (lazy susan bearings are pretty bad!) off the self.
For a big project a car one piece stub axle looks like an option (~AUD50):
After a bit of searching I found good candidate, a bicycle front wheel hub:
Are you excited yet? AlanX