Now, i have too, build my own control for playing with PiFBA mostly (i will add some other emu later) Is still rought (no paint or custom panel) but it's fully functionnal!!
I used a control interface from groovygamegear and it works like a charm.
Here some pics
If you have question, i'd be pleased to help, if i can :)
Nop but it would be a good to have for exemple 2 different mame, one for children (with cute game) and an another one with all other game :-D I will think about it thx ^^