1) Remove the level restriction from limited jobs but have a queuing restriction instead.
Like, let my Blue Mage reach level 80 already, let me farm FATEs, hunts, maps etc with it if I want to. But don't let me do the most recent raids/trials/dungeons with it until the next expansion comes out or maybe 2 patches later.

2) New job: gambler. Use your MGPs and gils to perform your abilities. Purchase new skills with MGPs. Most skills are RNG based, or have a different result based on the amount of money you are willing to spend. If the total amount of damage you dealt in one fight ends in 777, get all your spent money back. Get some MGPs as a weekly reward/first time bonus for completing each duty.