Those YZ80's were pipy little things. Unless your wife likes noise, likes to rev the piss out of things and generally ride old things agressively...that YZ is better for a kid who has interest in vintage things. (How may do? I have one of six who is)
Best wife bike's of the era were any of the PE175's, KDX175-200's, Yamaha IT 175's, Honda XR200's if you like Pacific rim iron. If you like Euro stuff find an old Bultaco Alpina. Tuned to where they start they were a great trail bike. For anyone.
One lesson I learned years ago about wife & kids. They don't enjoy things not good enough for me. If I like them, find them easy to live with, ride, and can have fun with, typically they do as well. If I find them hard to ride, live with, and operate; they will find them doubly so...
That ignition issue...ebay might help. I have an old Yamaha JT1 that needed a carb slide-damn thing wore right thru. I found an old motor and was able to savage the carb, clutch and other stuff as well. I would try to see if that ignition was used in various forms on other Yamaha products and then look to ebay as a source of parts. My bet is that ignition is used on several models. Any current or ex Yamaha dealer types out there who might know?