Additional thumb modifier key.

Hello! First time poster on the forums, so please go easy on me if this has already been brought up and shot down (A quick search didn't yield anything on this subject.) I currently own a Tartarus and love the "shift" button being by the thumb. It's quick and easy access for another set of hotkeys. Would it be possible to add another key there? Like a ctrl, alt, or both? Sure, I could probably set one of the other keys as ctrl or alt, but I'm extremely clumsy with my pinky and end up fat fingering everything.