While there might be more “important” ranks later on, you could always build around that by getting only the skills that you wanted. Like Grillo said, getting linker C2 an Thaumaturge to any rank would allow you to buff your party with anything you like and considering you go C2 Thaumaturge, you’d only be losing the current classes that we know of atm. If the player making this build doesn’t like any of the current classes for their Wiz build, then they’re not really giving up much.
BTW I’m not sure but don’t Thaumaturge skills stack onto all party members anyways? I don’t actually know of any buff that doesn’t go to all party members besides Divine Might and Self-Buffs from Archer and Swordsman.