Input display for PS1 and PS2 console is extremely difficult. It requires writing custom code, timings, packet sniffing, etc. I wish it was as easy as it is for older consoles, but it's sadly not the case.
Actually, my friend @zzattack makes and sells these. http://munia.io
I feel like necro-ing this thread wasn't a waste of anyone's time :p For an example, I would recommend checking out my latest Ape Escape 2 - Any% PB here on SRC
@Cravone Keep in mind the Input Display rule applies only for Emulator runs, if you play in console the Input Display of your controller is not needed, so feel free to submit runs with the PSX console.
Due to this game nature I kept stuff simple and without a lot of rules and settings to make it easier to run. Somebody asked me to be a mod and gave them access to work in the board changing and adding new things.
That person left the moderation some time ago (I never noticed that) so I'll be work