extend the press and hold app to other keys Thanks to this question: Customize accents when holding down a key

I know understand how to customise the press and hold app a bit to letters. But I'm wondering, could I do the same trick for other keys. For example if press the > (shift + .) I would like to get a pop up where I can choose to select → or ≥. Would that be possible ?
Okay, I think it is not possible, therefore I've made this little html app, that mimics the OSX app:

https://openuserjs.org/libs/kasperpeulen/pressandhold

You can find a demo here:http://embed.plnkr.co/jNA28BBb2JFAccPPX61p/preview