Yeah the new xml is bonkers.... I have a hard time making sense of it. I know the rom manger people are particularly peeved about it because the way it's presented some games look like they have a valid rom available when in fact they don't.
Anyway, it's easier to parse, but isn't necessarily any more accurate than the old version. As you stated games with multiple control types... well what is reported is up to the driver author... they might just pick one and use it, list all three or what have you.
Also which controls are counted as a control are also random. Joysticks get a control type as do any analog controls, but stuff like shifters are just listed as buttons.
It would be a lot of work to reformat the dat to something useable with the new versions of mame.
I think we'd have to post in the software forum or everything else when/if you are ready to go on it though. I don't know if you've noticed by this board is kind of dead.... it even took me a week or so to realize you have posted something.