Neither Charlie or his wife can just slide over in their seat a couple feet to make room for someone else to reach gear they are in the way of.
That slide alone can take a while while he positions his feet with his hands then moves his body with his hands. It takes time especially when each step may only move him six inches. There is no way I can think of to modify the boat to run all lines to behind the wheel. Even if this was done I don't seem him being fast enough to switch from one side to the other.
I took a friend of ours who uses a wheelchair to the Judd Goldman Adaptive Sailing Program in Chicago. She is completely paralyzed below the waist so I was certainly wondering how she would be able to do the things necessary to sail a boat. I was pleasantly surprised to see that, with only a few not too extravagant adaptations, the boats were easily sailed by two people with very limited mobility. One person at the helm - which was a sort of bucket seat on a pivot that allowed the person to move from one side of the cockpit to the other - and the second person, also in a pivoting seat, stationed at the front of the cockpit handling all lines, sheets and halyards which were led to the cockpit.
Here are some links to videos that may give you some ideas as to how you might modify Charles' boat to enable him to be more able to handle it.
JGASP :: Adaptive Sailing Program