The dead three lost their godhood because they trespassed the boundaries of what Ao deems acceptable behaviour. Their godhood was limited because it was subject to an overgod ending it. An unlimited godhood would be one that could not be limited by any other entity. Shar is a member of the Faerunian pantheon and could therefore not grant powers to others which she does not possess herself.
If the dead three want "absolute" power with unlimited meddling in the affairs of Faerun they would be forced to pursue a novel path to becoming a new kind of Deity.
I hope that explains what I meant

Last edited by ArmouredHedgehog; 13/11/20 06:52 PM.
I sometimes use thought experiments. I don't necessarily believe in every idea I post for discussion on this forum