Idea:

An ability to siphon entire party's mana (aether) by 75% to summon an almost full primal for crazy spike damage, sort of an additional limit break. They would have to time it strategically so healers and PLD won't be out of commission. That would definitely be "Strategy" as per the lore, and make parties want a SMN for very specific turns.

I'm sure there's possible issues with this idea, but it could strengthen team-oriented gameplay, while utilizing lore and the demand for more power from the Summoners out there.

Anyway, just an idea.