What political system would ISIS have if they succeed

Right now I see them as having a sort of feudal system, but say they took over a larger area and became a sort of global superpower with say, the territories of Syria, Iraq, and Iran. Ok, this is a what if so no need to blow the man down already. I know this is a serious subject but really there's not much to be done about it anyway so here goes.

I am guessing they come up with slave based economic system with a Democratic political system. Example?: The Confederacy.

Let me know if this is innapropiate to discuss.

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