Staged pre-orders

Would like to have a way to stage pre-orders so you have a special offer for the first X units. And after that offer expires (either by date or by limit number), the offer automatically changes to the next stage, and so on.

For example

Stage 1 offer: Available for first X preorders at $Y. Offer ends when first X pre-orders have been filled OR after a fixed date/or number of days. When this offer expires, Stage 2 automatically is enabled, with Z number of days duration at the new price. When Stage 2 offer is filled or times out, then Stage 3 kicks in at another price with Z days duration. To set the terms for the actual pricing a different product would be defined for each offer within Shopify. All we need from STOQ would be to be able to set up this multi-tiered/staged pre-order setup.