I went with this:
Vaan- Shikari / Foebreaker: Daggers can apply status ailments, and Foebreaker allows for heavier armor (not really necessary) and the most useful technicks in the game.
Balthier- Uhlan / Machinist: So much for flying enemies.
Ashe- White Mage / Time Battlemage: If I had to do it all over again, I might split this out, since Ashe had quite a bit to do. Then again, it made her far more than situational, especially in the late game in some of the more dangerous areas.
Basch- Knight / Bushi: Combination attacks galore
Fran- Archer / Red Battlemage: Decent damage and spells + Ardor. I used Fran as my player-controlled character to keep her at range.
Penelo - Monk / Black Mage: So broken it's not even funny. She's easy mode, since black magick is overpowered. Oil + Firaga == dead damn near everything.
This party made for some obvious Esper bridges. Penelo could use curative magicks, Fran got upgraded spells, etc. Espers themselves are still useless; just not as useless as vanilla FFXII.
Levels don't really matter in FFXII. Licenses are so much more important. Most of the tricky hunts and Espers have some sort of gimmick that can be mitigated with equipment and proper gambit planning. Case in point - Yiazmat fell within 30 minutes (at 4x speed) after I survived his opening salvo long enough to apply the Wither/Addle/Shear/Expose debuffs. (Of course, the game makes you earn the most powerful magicks/technicks by putting them in dangerous areas.)
The final boss is still a bastard, though. I had far more trouble with him than anything else the game threw at me.