Was wondering why P2Start wasn't working.
It's because of mame2003\cfg\default.cfg files all over my roms share.
In these I overrode p2Start to hotkey button press for 1 joystick controller with button set.
Now that I have two Joystick button sets this override is bad. It ruins behavior.
So create a new original default. Propagate that all over.
We still need to deal with mame menu hotkey press and swapping button a and x.