Don't know if this is still being updated, but I'd suggest Chel, from the Road to El Dorado, as a medium addition.
Scarlet Witch (with Quicksilver), Dagger (with Cloak, 2013 Ultimate editions), Stahma Tarr, Pyrrha Nikos (with Sun Wukong)
Chosen, In Planning:
Red (with Subject Unknown), Tempus
Ravager, Sakhmet (with Inanna)