I agree with OP. Every job is a more specialized version of a class anyway, and once you're BLM or WHM, or PLD, or WAR, - why would you go back to being THM, CNJ, GLD, or MRD? It seems like every class eventually ends up as a job anyway, so why bother with having both?

I'd like to see something like FF Tactics where once you are a certain level in two jobs, you can unlock another job. If you're WHM and PLD, you can unlock white knight for example. It would be awesome if when you get two jobs to 50, you can unlock another job. WHM and BLM would unlock summoner, MNK and BRD unlocks thief, BLM and WAR unlocks DRK, etc.