Absolutely! If you don't want a second copy of the game included, just add the difference of the game to your pledge ($52 CAD, about $40 USD). When they survey is sent for your custom squire, you can add the details for both f your custom cards!
Unfortunately not. The box is a pre-set cut that securely fits the 18 cards. (I have been able to add an extra card or two however, but I can't guarantee the bonus cards will fit 100%).
If this changes, I will update everyone!