Hmm…
It's a good idea, but a Minimates game doesn't quite have the appeal of a LEGO game. Here's why: a LEGO game is much more ‘buildable’ than a Minimate game. LEGO Star Wars, for example, has the Minikit concept whereby you can ‘build’ replicas of spaceships and other vehicles, then use them in mulitplayer arenas. In a Ghostbusters setting, you'd be able to build expansion packs for the ECTO-1, a full ECTO-2, ECTO-4 (from Now Comics), and, if you prefer, a few of the vehicles from the Kenner line. Also, there's the possibility of destroying set-dressings and then rebuilding them in different configurations–a refrigerator, for example, could be rebuilt as a grapple (or Slime Tether in this case) point.
Dialogue scenes rendered as games of “charades” would provide for much humor as well.
I think Possessed Dana and Gozer would be hilarious, yet more-than-a-little-disturbing, if rendered as LEGO characters (cf. Leia in Slave Girl costume).
The only question is, does the world of Ghostbusters have as much potential for loosey-goosey fun as Star Wars, Batman, or Indiana Jones?