To be able to sequentially book orders and seller still appearing in the search page. So, there would be always a maximum of parallel orders, but buyers who don’t mind to wait can order to some specific buyer (instead of not finding him/her, or go to his/her saved gig, but found on hold and must return again)
Buyer A make an order to seller A (with max. sequential orders = 1, so now the sequential queue is full)
Buyer B searches for some gig. Instead of not found seller A’s gig because overbooking, find it and like it, but with a label: something like “next order for 5 days maximum” (but it will be usually less, I’m counting the “This order will be marked as completed in 3 days” thing)
Buyer B prefer seller A’s gig for some reason and doesn’t mind waiting: makes order to seller A, but deadline won’t start at this moment.
When seller A delivers his/her work to buyer A and this one confirms it, automatically, a new order (the one that buyer B made some days ago) is active and the deadline starts from that very moment. Buyer B didn’t have to wait until the gig from this seller appeared again.
Of course, there could be an option on the search page for buyers for searching, for example, “only immediately available sellers” if they don’t want to wait.
Let’s control that flow of orders!