Could make Ramuh a stunner/buffer. Has an aoe stun Shocksquall, an AoE buff - Enthunder which gives everyone a small amount of damage added to their autoattacks, maybe Hastega which would be a 5-10% bonus to autoattack speed. Leviathan can be a healer, Spring Water would be like a Medica II centered on him and also remove some debuffs(only poison blind slow paralyzed heavy). Can give him Tail Whip which would be an AoE damage+20-30% slow for 20sec, Aquaveil an AoE Surecast, long recast though like 180-300s, Tidal Roar would do small damage on single target but reduce their damage by 15%. It's hard to make them all different without making SMN kind of a hybrid RDM type job.

Also if they release shiva leviathan and ramuh, SMN will need a Tridisaster II haha.