Or if they really want to screw the green dice, make it a week long entry into a lottery pool. Put scratch away codes on the back of the bye cards for exponentially more entries based on whether it's from a store championship, regional, or national and hen let the computer decide.
Give regional and national winners good enough odds that they'll most likely make it and have dedicated spots for past top finishers at worlds.
Any system is always going to screw somebody.