With the level cap, introduce a new job system which requires you have 3 classes levelled.
You could easily have DRK made from ACN, LNC, and GLA or a WRK : CNJ, GLA LNC

Also, could you weave in the DOH classes into this and make it interesting e.g PGL+ALC+ACN = Thief with skills based on reagents almost similar to rikku with a dampened down mix mechanic.