Heard me out before you rage.
  1. Make raids Job-only.
  2. Introduce cross-class skills that aren't tied to any class but are instead learned from Grimoires, Allagan Tomestones, ... etc. (i.e. "skill books") which are acquired from quests, vendors, dropped from NMs and appear in their own classless category - they are of course for use by specific classes only.

What is the point? Decking out Classes can be another activity you can do in the game. You have a nigh free hand in how you want to configure your class.

Since raids will be Job-only, which they already are in practice, balance with Classes with their high degree of freedom when it comes to configuration won't be an issue. SE can go wild with cross-class skills. Who cares if it ends up a tad broken? No one is going to be kicked out of their static's raiding group.