Ideally, Ninja would make more sense as DPS, with Samurai as the tank (I'm thinking like Auron from FFX). Musketeer/Corsair would be its own class/job, and Ranger would make for a great physical-oriented branch class for Bard (maybe lose the songs, gain more offense/defense/aoe techniques)

I really would want Red Mage as a job to be based off its own class, but a GLA 30/THM 15/CNJ 15 could work too. As for Blue Mage. . . LNC 30/THM 15/ARC 15? (I don't remember enough about Blue Mages)