Bard or Machinists

[Anova]

To me, both will apply buffs and debuffs. Bard is very well known for their ability to buff mp regen (great for white mage in general) and debuff enemy magic defense (great for black mages and white mage holy spam). The only difference is that the buffs/debuffs move with the bard, whereas machinst places stationary turrets for their buffs/debuffs.

If you want to be unique, you're out of luck. Bards are the most popular dps class. This might change in the future though since everyone's going to be trying out the new jobs when the expansion hits. Sticking with bard might make you an outlier in that regard. Also, Bard players are likely to split between Bard and Machinist as their favorite. Try both out and see which one you prefer. Bards and Machinists will be competing with each other for slots in static groups and premades, but it shouldn't be bad.

The way the game is designed, new jobs require you to talk to the associated job npc to unlock. This is true for rogue/ninja, who requires players to visit Limsa Lominsa to unlock it. If you start in Ul'dah, you don't get to unlock it until lv.15, whereas players starting in Limsa can unlock at 10 (when they can class change). Considering the job npcs for the new classes are in Ishgard, you will have to find a way to get in to Ishgard without completing the 2.5 story first.

It might be possible if a friend flies you there through some unexpected backdoor, but you will not be able to walk through the front door. In other words, you're relying on a glitch or bug to get in to Ishgard before completing the story (which does have some pretty big spoilers). Given SE's QA department and the game's previous history with a lack of QA (remember 1.0), I don't expect that backdoor to be easy to find.