Adding features to the RDS encoder isn't that difficult (there are clear specs out there). But I usually add things when people request them because they need them for something... do you need these things?
For example I saw this description for PIN:
Program Item Number (PIN)
Identifies the scheduled broadcasting time of a specific program. It enables an RDS receiver to work on specified programs
only. This function can be used to plan recordings on scheduled broadcasts.
Now, in this day, does anyone use that? Who records radio programs when you can usually look up every fragment online? What devices support this?
in more modern countries you can find most of the programs online but in Slovenia you still cant find all the programs online (and even if they are out there you have a hard time navigating through all this web sites layouts) so PIN would be very usaful to just simply record the program you want
PTYN is nice because you can name specific music programs for instance PTY: Folk and PTYN: Balkans would indicate specific Folk Music (there are a lot of difrent Folk Music like Dutch, German, Slovenian, Bosnian are all Folk Music but are diferent
ECC is nice because you could quickly know from which country the station is without looking the PI code up on FMlist
so if you could implement theese I would be realy happy and would definitly make a lot of use from them