Thinking on other Final Fantasy titles, something that could be interesting, and maybe could provide some SMN-BLM synergy is Vivi and Steiner's magic sword ability.

In FFXIV terms that could be translated into something like adding a damage up percentage to all weapon skills of all party members around target party member (basically something that can hit all the melee and tanks) and changes all damage they deal to magic damage (as opposed to slashing/piercing/blunt). This could encourage a new party comp with BLM/SMN as the two ranged DPS if you can coordinate that skill with Contagion from Garuda.