I sorta wanted the same..I at least wanted to try to play all basic roles so I understood my main (Bard) better.
I ended up liking healing much more than I thought, so now it's my secondary. But yeah, I say give all the roles a try. Sometimes you'll know if a job isn't for you (I still hate MNK...sorry monks) and sometimes you'll fall in love with a role.

And what File2ish said, roles can be very different. I don't like DRG but I love NIN, and both are close-combat melee. Same with SCH and WHM... I'm an all right scholar but I can't WHM myself out of a wet paper bag.

And with tanking..I also hate it. I got my PLD to max level because I said to myself "I still need to give this a shot". I'm glad I did. Am I going to continue to level it? Mmmmmm probably not. I still hate tanking. But now I understand it better, why certain tanks do things...why certain tanks DON'T do things. It also really helps as a healer.