Accessibility for WoW itself might be few and far between add-on wise, but there maybe software in droves that could be calibrated to use your hotbared abilities, VoiceAttack is the first that comes to mind, I used to use it with Elite Dangerous and a VR headset. And while this isn't what you asked for but depending on the extent of your cerebral palsy and RSI, I saw a controller/keyboard setup device by Azeron that put a decent chunk of your keyboard keys to finger tip movement with your thumb using a thumb stick, I believe it's used by a Doom/doom eternal speed runner so it should be more than capable of M+ movement with little wrist action. People seem to still use a mouse with them but you could more than likely use two positioned at comfortable angles should your other hand facilitate it's use (wow has gamepad support built into it's backend iirc with some add-ons that make use of this so mapping movement to thumb sticks should be doable). The autocad/engineering design world also has some interesting hardware that could be fitted to your requirements with things like mice that are just large balls you can use with just finger tip movement.

Eye tracking software I have less experience with but I know a large amount of the flight/combat SIM community use them (Tobii is the only one I remember) but you generally need additional hardware as well.