I think instead of changing Summoner they should keep it as it is, and then make a new class called Evoker, which would do things like a classic FF summoner would. It makes sense to me. As a summoner, you're summoning the presence of that primal. As an evoker, you're evoking (or invoking) the power of that primal. Slight difference, but in the Evokers case they're just unleashing a single brutal attack, like Diamond Dust.