Put simply, you have three options: extract and edit the game files so you no longer need to pass a power check; open the Ren'Py console and edit the variables so you pass the checks; or just give up and either no longer use that power, or start a new game.
I've attached a modified combat_player.rpy (7zip). Copy it to the game/combat folder after you unrenpy it. As
@MisterAnon04 said, this should only work for the current version of the game. You can use a diff tool to see what was changed if interested.
Editing variables via the console might be easier - the current code tests that only ONE of the following variables is true:
powerTg2 (Gender Quick Shift)
powerTm2 (Advanced Cognition)
powerTs2 (Advanced Bone Structure)
powerTp2 (Advanced Musculature)
So set the one you like best to True, then all others to False.
As a disclaimer, this is just by reading the game code. I suspect other areas of the game may be protected, so cheat with moderation... or use an updated mod.
-T-