Yeah but being this philosopher, mentor type character makes him perfect for a supporting role... almost Morpheus-lite.
With Black Bolt you've got the awesome, mysterious trump-card, with Medusa you've got his anchor and the one that ties him into the rest of the group.
All three of them probably work best "guiding" the lead, helping them find their footing. So do Triton and the guy with the hooves (can never remember his name
Crystal is the most "normal" of them all, the one whose emotions and personality are most grounded in honest humanity. She's almost a mix between Wolvy and Rogue from the first X-Men movie, and the only one I can see working as a window into their world.