RTF is a global modification that replaces all towns in the game.

Maybe give them the Summon Elementals spell?

That would be good, but then the elementals themselves should be made a little weaker than other 6th-level creatures, otherwise it would be an imbalance. And in general, since "Elementalist" is the name of a hero, let it be called that (with upgrades, etc.).

Summoner - master of the elements - spellcaster of matter...

You could, of course, also use genies, but... they don't really fit with the theme of elementals.

But summoners would. These are mages who fled from the silver cities and found refuge among the guests from the plane of the elements...