In reply to ironbark:
The walk-in requirement is the killer here.
Aonach Mor is still a walk up 500m vertical unless you are allowed on the Quad. Then you get up there and you find that, for beginners, Easy Gully is a formidable obstacle. The run-out is neither welcoming nor easy to access.
The bottom of Coire na Ciste is about 800m vertical, minimum. It is good for the purpose and if it all goes pear-shaped there are loads of folk around, MR kit/radio nearby and its downhill all the way home. Best of all though, it is a spectacularly beautiful place for a person to experience their first proper winter day on the hill.
Coire nan Lochan in Glencoe might be an option. Much the same category as Coire na Ciste: big walk, good, beautiful.