People keep mentioning that this cab (with the rotary sticks) will add more complication to the MAMEification. If he wants to play Ikari Warriors, any cab is going to have the rotary complication. If the games he's most interested in playing have rotaries then he is closer than the rest of us from a hardware standpoint to making it work.
Also, I dig the idea of preserving dedicated cabs if they were built as dedicated cabs. Games that shipped in generic cabinets don't lose much inherent value (I don't know about financial but I mean real value) being pulled from their cab.
Anytime someone says they are looking at a flat-pack cabinet we say "no, no, build from scratch, you can handle it, it doesn't take much to learn how" but someone says "hey, can I convert this rotary stick game cabinet into a MAME system for rotary games?" and the response is "no, no, it's too complicated"?
I think if you're concerned about the preservation of the cab and it's art, leave as much of it intact as possible, use jamma or custom harnesses to reversibly make the wiring work to an encoder and video card and then fire it up as a MAME cabinet specializing in the games that work with the native controls. That's my plan with my magical spot (of course I don't have an original board in mine.)