I guess that's up to the manufacturer but there is a definite void for high quality rtr coaches to run with several of the A classes that will emerge very shortly. The Cravens have been produced by MM but only in BnT livery.
Park Royal coaches were introduced about 1955. I don't recall off hand if they were ever liveried in silver but certainly in green and later in BnT. There were two variants mainline and suburban.The Cravens were not introduced until almost a decade later, hence their modernity, leaving Silver, light green, dark green, and potentially early Black and Black with yellow panel A classes without much in the way of rtr rolling stock. I suspect a PR coach in green and BnT would be worthwhile for a manufacturer to produce.
I suspect a rerun or updated Cravens might sell too. There seems to be some market but I don't know how large. Personally I have 2 rakes of Cravens so I probably would not buy more but I understand newer modelers may have missed out and these are now sought after by some.
As for CIE built stock, I'm not sure. IRM took the 42' flat chassis and placed a ton of difference freight options on top. Most were modern era which may be more popular. A 61'6 coach chassis with various bodyshells in several liveries that lasted over 30 years might be possible. Personally I need rakes of them but I really don't know. We live in hope for those thing and of course 21mm track