Can auto-coupled approach procedures involving Radius-to-Fix turns be performed with non-GPS nav-aids or some combination?
In the case of DME and IRS, will the FMC generate some usable combined output during an RF leg?
The ability of an FMS to fly various ARINC leg-types -- e.g., TF, RF, VA, CF, etc. -- is entirely separate from the position computation function.
Either the FMS can fly an RF leg or it cannot.
The sensors used to compute aircraft position are not relevant.
Having said that, I'm not aware of an FMS that is RF-capable that does not also have GPS sensors in the navigation array.