I prefer the idea of Psionic having some exclusive abilities instead. A problem of PS1 is that was too easy to have similar class builds IMHO, while each Class should show more differences, like in all RPGs. So even using the scaling cost idea, a Soldier should NEVER be able to reach a Psionicist level of skills in Psionics.
About the hero thing, I am planning to have a set of unique abilities for each character, and that would obviously include the playable character (hero).
