This discussion relates purely to those kinds of RNP based procedures, and is a subject for which no current BizAv based avionic system, as typically used in any RJ presently flying, comes anywhere close to meeting RNP.1 capability
Huh? Numerous business jets today are fully certified for RNP 0.1 approaches (including those with curved segments). E.g., Gulfstreams equipped with Honeywell Primus, Bombardier Global series (with Rockwell Collins), and Cessna Citations (Garmin) all include full RNP 0.1 approach capability available as options. Some, like Cessna, include RNP 0.3 as a standard feature.
So it's not a technology issue but whether or not specific customers require (and is willing to pay) for the capability. The reality is that new business jet avionics tend to be
superior than your typical airline fleet avionics.
In Europe, trial RNP curved approaches were conducted on a CRJ-1000NG operated by Air Nostrum.
Since you mentioned PAJN, note that Horizon has been flying curved RNP 0.1 approaches there on their Q400s, mere turbo-props!
And in any case the refreshed regional jets coming up (Embraer E2, Bombardier CSeries, etc) are all orderable with RNP 0.1 as options.