I've seen a few ideas for a Portal AU with GLaDOS!Tadashi and I fully support the idea, but with a few changes. Like what if Hiro was the test subject and the voice of GLaDOS sounds suspiciously familiar to him yet the robot doesn't allow him to speak so he's always silent while testing, only talking to himself. Only when he finds out that GLaDOS wants to kill him he starts talking to him and the robot has some malfunctions and gets angrier because Hiro's voice sounds too familiar to him.
*makes sad noises while flailing*
Because, like, OH MY GOD HIRO’S GOING TO FIND OUT. He’s gonna beat all the tests and traps and whatever GLaDashi can throw at him because he KNOWS his brother, knows how he thinks. It’s easy for him to predict what’s coming, even if he doesn’t know WHY it’s so familiar.
But then he makes it to the center. Then he sees what Aperture Science did to his brother.
OH MY GOD WHAT WOULD GLaDashi DO??? Because like, he wants to kill all the squishy organic humans after what was done to him, but it’s HIRO. TURMOIL. He’d probably have to ditch all of his old personality and love for Hiro into a personality core so he could fight Hiro properly, and then HIRO WOULD BURN IT DURING THE FIGHT AND AAAAAAAAH HE ESSENTIALLY KILLS HIS BROTHER BECAUSE HE CAN’T STOP WHAT TADASHI HAS BECOME AND HE NEEDS TO ESCAPE AAAAAAAH.
(or somehow he kidnaps the personality core containing Tadashi’s old personality and escapes with him, after destroying GLaDashi. And so he gets his brother back, albeit as a personality core. They can work with that)