I have no problems with having the option to equip any skill, at any time, on any class, as long as you've unlocked it. Having all options available increases the players own self expression, hence their uniqueness. Same goes with gear. The more restrictions you impose on the player the less unique they become. The best they can hope for is to be accepted into whatever clique (jobs) they've chosen. That does not enhance uniqueness. Let your accomplishments set you apart, not what you wear.
If anything, positively reinforce the player to equip a certain class of abilities i.e. add a buff if they've equipped abilities within the same genre. Then incorporate a naming system that is representative of the classic jobs. Don't restrict the player from locking them from what they've already earned.
Certain artists gain accolades because they demonstrated a unique look at their given medium or made self imposed restrictions. Without having all the tools available to them, their accomplishments are stifled. What a person chooses to do and what not to do gives them their uniqueness. Jackson Pollock is very different from Piet Mondrian. Let the player decide who they want to be. Let the context decide the best course of action. Let the community define its cliques, but don't repress the individual.