Either...
1. Standard double-joystick pattern, joystick-spread of 6 buttons-joystick, total width being around 12-14".
2. Modular.
3. Swappable panels.
Those are pretty much your only options. Shifting everything over to the right's going to feel weird. Your natural inclination is to center your body to the controls, shifting to the right means your body is almost going to have to turn to center itself. So you'll either feel like you have a weird neck position or hand position, and it's not going to be satisfactory.
TBH, I'm becoming a big fan of modular design. It's a bit harder, but the payoff in not making comprimises is worth it IMO. Additionally, that design allows you to add a trackball or spinner down the road if you find yourself wanting one, without forcing a complete redesign and rebuild. Sacrifice is a small increase in cost, and an initial investment of more time, plus no artwork.