Brian: you have to understand, the ideological purity of MAME is widely believed to be exactly why it still exists while all the others have fallen by the wayside. MAMEdev has repeatedly encouraged people to use RAINE instead (which is far more user friendly) but people refused and it's dead.
Furthermore, there are separate projects to handle that - look up "controls.dat" and the Windows programs "CPViewer" and "Johnny 5".
J5 in particular is quite nifty: see a few screenshots here
. You can program it to know your cabinet's buttons and it'll auto-label them for any game it knows about.
Obviously that doesn't directly help you, but a lot of frontends implement that support now too on the Windows side so if MacMAME ever gets split in 2 that would be an ideal feature to add.