I have a Mavic 631 Starfish crank I pulled from the wreckage of my Tommasini. I also have the rare Mavic triple adapter for this which I never used.
I was cleaning this up and installing the triple adapter for possible ebay sale when I had a big idea for the Bianchi Grizzly I'm working on:
This is just draped on the spindle ends, not mounted. Looks pretty buff to me, although the big chainring is a little large.
This is a pretty low tread ("Q-Factor") crank, so I don't know if I can make it work on a MTB and still get a good chainline. But it looks like it might be worth trying.