There's an easy way to fix this. Well, easy to conceptualize, not easy to get the company to agree to. Add a condition to the reserve-required formula that says that the reserves required for any given day in a bid period can never be higher than the reserve days awarded to that day via PBS, minus one.

Excepting the bid massaging timeframe, every category would open with every day as blue, and as people adjust their schedule (except for people dropping reserve days), the total number of reserve days in the month would stay constant. If one day gets lower, another gets higher.

This change would also incentive the company to adequately staff categories, because if they don't have enough people in base and/or assign enough reserves, the rest of the category gets a free for all to change their own schedule, including dropping.