A mixture of the old cross-class and the new role-actions could be interesting.

Level up in role to unlock the role action, classes can use all unlocked role actions, jobs can use role actions from their main role and their closest thematically linked role.

So Paladin can use tank and healer role actions, Dragoon can use melee DPS actions and tank actions, White Mage can use healer and ranged physical DPS actions, etc.