The first idea I had was to create a list of common creatures that are legendary for sake of the format. That seemed overly complicated. The second was to just create common legendaries for pauper, but that seemed like too much work (and I am doing this more as it's neat to see if it could work rather than actually try to make it happen). The third idea (which I think is best) is to allow any legendary creature that has been printed as a common or an uncommon. This allows for a pretty decent list of 143 commanders, and many more possible combinations with all of the new partners. (Basically this allows for any card printed at common or a legendary creature printed at uncommon to be in the format)
|[card]&type=+[%22Legendary%22]+[%22Creature%22]]Uncommon, Common Commander Search
List of Commanders
Approximate Total Cost:
I also included a few other "tweaks" to expand the roster of commanders a bit. First, flip cards can be your commander if the flipped side is legendary. Second, for Brothers Yamazaki, you can have two copies as your commander, and any deck with a red color identity can play two copies in their deck, because this needs to happen just because.
Overall it's a pretty diverse list with a bunch of interesting (and some not-so-interesting *cough*Legends*cough*) options, including a three three-colored commanders thanks to Masters Editions.
Overall I would be interested to hear other people's thoughts on this idea.