It would be cool if Ifrits used a random fire spell.
The Ifrit Sultans in the mod are an alternative to the Pit Fiends. While Pit Fiends are casters and not very fast... Ifrits don't have spells, but they are highly mobile and have high initiative, and they deal 20% reflected damage. Overall, Ifrits are as balanced as possible in relation to the heroes from Heroes of Might and Magic III.
That is, vanilla Pit Fiends can cast fireballs, but the modded Ifrits have a different focus.
So, by upgrading the Pit Fiend building, you can choose whether to use Pit Fiends for casting or attack with Ifrits.