If you could adopt and adapt a system from any FF title...

[Zetsumei_Tsunarashi]

This is my concern with blue mage. I haven't really seen any monster abilities that make me think, "I WANT THAT!"

There's few cool ones. Hippogryph has the Aoe stun. Raptor has the fire breath. Chigoe has that AoE Bio move. The toad tongue thing would be cool. Dodo has sleep spell. Pieste has petrify. And of course there are the classics like Goblin bomb toss, Malboro bad breath, and Bomb's self-destruct. And If I could have shadowsear back from dodore, you know I would get it lol

[Alerith]

Junction system!

[Zantetsuken]

Job tree from FF Tactics + the 'Learning spells and abilities from gear' system in FFIX

Oh yeah, and FFXII gambits were awesome -- I remember wishing the NPC fellows had something like that in FFXI...

Maybe our battle chocos will get it?

[shawnmb]

FFXI auction house.

[Fear]

FFXI auction house.

We're getting an AH in 2.0

[Addicted]

FFX Blitzball mini-game up in here.

[Scotchio]

Maybe a Beastmaster job that instead of just charming mobs and having jugs like in FFXI, use a version of the monster capture and infusion from FFXIII-2.

You could build a few different pets for different situations.

[Arkine]

Any battle system that isn't based around a gimmick and/or has reasonably working targeting system. (or just FFXI's... that was a solid system)

A not-based-on-luck materia system.

[Deltara]

Campaign, Fields of Valor, Moogle Augments for Gear...

or a system where i don't need 7 other people just to get out of my bed in the inn.

In short, maybe some content revolving around light party.

[Psion]

Puppetmaster (with h2h combat please ;-; ) + FFXII gambit system for the automaton.