Also I might make Pent free because otherwise whoever has him as a big advantage, since he has like twice the Warp range of your healers, especially since they can't even promote.
TBH I think this draft idea is inherently imbalanced- free Marcus solos the game, but if he's not free, then certain draft picks give an almost unbeatable advantage (Pent, and to a lesser extent Isadora and Farina), due to the lack of versatility in picks.