My understanding was /is that they didn't go RG because of the certification costs (both in money as well as time-to-market terms). Designing an aerodynamically efficient a/c with a big engine seems to have done the trick. OTOH, though, to my knowledge you cannot certify a fixed gear piston for FIKI, at least there doesn't seem to be one out there. So, from a IFR touring POV, there should be a case for an RG variant.