It’s not as easy as dismissing the annual bid. The annual bid came about because of the quarterly bid’s incompatibility with vacation bidding. If you lose vacation moving to the quarterly system you’re bidding after upgrade whatever scraps are left…. Which is October or September. If you let people keep vacation, then you leave the fleet without coverage and you somewhat subvert seniority.
Its not as easy as just switching to a new system. The supplemental bids are for ad hoc adds and thus the vacation impact isn’t as great.