Back to topic. It would work best to play the class you want. Going by what you've said though, I think you will like the way tanking works in the game.

FFXIV boss fights are very mechanic-heavy, and the tank will often be responsible for directing and dodging aoes. As the tank, you'll definitely be in the spotlight a lot more. Some players like the responsibility and attention that comes from being the tank, others hate it. There's a reason many players don't play tanks at endgame, although they're willing to play dps and healer. It's just something to be aware of before you decide to main the role.