Again, the Guardian should have been Orpheus, he's the most obvious contender in terms of the player trying to figure out things from hints in lore drops as they play.
He has the inherited power to neutralize and control Illithid powers, and it could have been like one of those things where a character is imprisoned but finds a thin backchannel for communication to the outside world. Then you've got clean distinction between the adversaries (and after all the gith are depicted right at the beginning as adversaries of the Illithids), with the only funny business being him trying to fool you (the sex would have been weird, but after all there was no reason to have any of that nonsense at all), presumably because he thought you would be more liable to believe someone you had more of an affinity with (a dream figure representing whatever ideal of beauty and/or wholesomeness you have, which is after all what's offered in character creation).
It could even be him offering the powers - he has a visceral loathing of all things Illithid obviously, but he doesn't really care about you as such, and if you want to gorge yourself on tadpoles and get superpowers, he wouldn't care, so long as it makes you powerful enough to break him out, and he has the ability to grant it if you want.
You could then scale things back to the point where Goretex and the other two aren't main adversaries backed by gods but more of a spanner in the works at an earlier stage of a much simpler, less adversaries-heavy plan, and is using Orpheus for his fiendish plot to create an army of Illithids under his control. The scale would be right then because their motivation would be human-sized (dominance of the Sword Coast), but the big reveal would be that they would be being used by higher powers with more cosmic agendas in mind, currently unkown, which would prepare the ground for a "Moar epic sequel" to go to level 20, much like the Mythic thing of PF:WOTR.
I dunno, anything but this clusterfuck of baddies and mysterious personages. The Illithid/Gith rivalry should have been the primary axis on which things were developed, it's looking now like they're just some fucking joke in an over-complicated, over-fussy plot.