Hi! I checked http://www.morepas.org/software/mtocpp/docs/index.html for a FAQ (couldn't find one; might be a useful thing to have there) before asking this: does mtoc++'s output "play nice" with Matlab's "Display Custom Documentation" features?
Never mind, just answered my own ?: you lose all the field keys! Plus, struct2cell isn't recursive, so it only flattens the top of the tree. Still, it gives me something to start from. If I can write something that works robustly, I'll post it.