What are the three buttons at the top corners for? I assume one is your pause/shift key and the other is coin, what's the other one for?
For mine, I didn't give the other players an option for a shift key, and you can also map the shift2 key onto shift1. Then, for all the controller keys (enter, tab, ~), just make them shift keys somewhere.
I also concur to use another existing set of keys for the mouse. If you have a tornado spinner, that gives you three mouse buttons instead of two the optipac gives you (not really useful, but to some it might). I always like to keep spare inputs around for certain things such as duplicating certain buttons (like coin for both button but also for mechs). I'd rather not double-wire an input, but it can be done of course if you have low enough guage wire.