Replacing the Ruin and Tri-Disaster keys in order to free up space for more abilities sounds sensible, maybe Blood Pact: Rage/Ward from FFXI or one-off summons. Ramuh egi does have a model in game to my knowledge but at this point...maybe lets just skip to full summons. Seeing as how Phoenix is another person-turned primal like Shiva, I don't see any good reason to not add her in the future.