I would be more supportive of a payscale that is salary based - ie get rid of this "per hour" stuff all together.

If you pick up flying on your days off, it would be paid at an override of your "day rate" that is figured out based on your salary and "days available".

IOW, $30,000/yr salary, 14 days of work per month = $180/day, pick up a day trip and it would be worth $270.

Of course, contract language would have to be drafted that would increase the days off because the company could schedule 14-16 hours per day of "use" out of you (and they would, otherwise if they built pairings with 4 hours duty time it wouldn't be very efficient).