[The Procrastinator]

If you plan to train your bishops, I would make sure they both have access to the charm and knock knock spells on different schools, which would eliminate the priest/psionic and mage/alchemist combo. If you want to have a good spell points distribution between the six realms, combining alchemist with psionic seems a natural choice, which would mean your other bishop would be a mage/priest (that would be a terrific combo for divine spells). That's what I would do, but I haven't try a double bishop party yet.