I was thinking about a control panel redesign recently and was contemplating the following button layout. It's a slightly rotated NEO-GEO, that also provides a wide two-button layout, a triangle up and triangle down layout, a diamond/Vanguard layout, as well as be good for many emulators, NES, SNES, PSX, PS2, with the diamond buttons and the other two for a L1 & R1.
If needed, I guess a thumb button could be added. That would help with the MK series as NEO-GEO buttons 1 & 2 would do the Punch, 3 & 4 the Kicks, and the extra thumb for blocks.