I was wondering if the software supports dual X carriages (two extruders, on the same Y rail but with two X motors)
How would you choose which extruder you want to manually move in the machine control panel?
I would assume that the different X-axis carriages are controlled via the firmware, probably by selecting a different toolhead to move each carriage. So in that case, it should work fine as long as your firmware is configured with the correct offsets and all that.
It's the exact same case with the BCN3D Sigma. And the Sigma is working five with S3D. The Sigma is based on the Marlin firmware, and the toolchanging process is manage by the printer and not in the GCode.