1) Build up your team with different NPCs you find across the world. You can also buy their contracts with MGP.
2) Every NPC will have a "star" rating from 1 to 5.
3) Set strategies ala football manager.
4) Compete against different AI teams (Ul'dah's Burners, BrassBlades, Illumanity team, The Un-Tempered, Costa's Warriors, etc)
5) Have a different competition modes: Tournament (once every two weeks like Triple Triad), League (monthly), Exhibition (Regular match with no impact whatsoever), PvP (Duh)
6) Winning or losing match would give you Blitzball experience enabling you to level up: Access to better tactics, getting better NPCs, better MPG rewards.
7) In addition to your experience, the NPCs would also level up separetely depending on their participation in the match, increasing their base stats up to their cap based on their rating.