A new "systemtype" tag in the -listxml output would solve this problem. Frontends could build a games list containing arcade machines only.
From what I could see in MAME's source code (drivers), arcades games have "GAME (game details)", console/haldheld have "CONS (game details)" and computer games have "COMP (game details)". It seems that MAME doesn't know the difference between console and handheld as they are both threated as console.
I don't know if it's easy to add to -listxml but it could be something like this: