There are lots of controllers that have more than 16 buttons... GP-Wiz 40, I-PAC Ultimate, Stream Deck, X-Arcade, etc.
In BigBox, there are 45 different controller mapping options, e.g. "Show Ratings".
For those of us who want to use BigBox with a stand-up arcade machine, we don't want to use the player buttons to control the system interface, so we set up a separate control panel for navigating games, viewing high scores, etc.
I really like BigBox, I'm just not sure why this seemingly arbitrary limitation was set.
-- Jeff Sorensen