I don't know if it has been mentioned before and it definitely isn't a pressing issue but maybe offering some kind of interface for developers to read information from RuneX would be cool? My original thought was that I wanted to create a trading post web app that showed trends and offers on the RuneX TP. I think that a lot of cool fan projects could arise out of an API.
I guess the main concern would be how privatized the RSPS community is, but with an idea like sharing trading post info you are only sending out data that can already be gathered in-game. Thank you and merry christmas