it isn't necessary for each primal to be associated with an element. there is also no reason to believe that each primal is restricted to any number of elements either. some of this may have been done for the sake of familiarity, but outside of the elemental based Primals, it is safe to assume that anything goes.

seeing as summoners can bring forth essence of the primals, it opens up a lot of possibilities for future summons for them. unfortunately, in 11, each summon had a strict association and the danger here is to use that as a template.