What do you mean by led support?
You know how in Atari games, you insert a coin and then the first keyboard LED flashes on and off? And then if you insert a 2nd coin, both the first and second keyboard LEDs flash? That's what I want, but for all games, not just Atari and Pacman.
It's supported in some older versions of MAME but then at one point they decided to disable it for game that never had lit start buttons in real life. I'm sure adding it back in is just a matter of tweaking a couple lines of code.