Just a suggestion in case it helps:
- Make a list in order received of the cancellations.
- Mail the customers to ask them if they wish to commit to buying when stock is available or would like to go elsewhere.
- Give them until xx date to confirm via reply that they wish to take part - make it clear any NDA restrictions, time they have to pay, what happens if they don't pay etc.
- When you get a delivery OR all up front now, run down the list and call people to sort orders OR setup a private website link with however many are allocated and send it to the first xx of customers, leaving it live for xx hours as per step 3.
- Keep people informed. Hell, do a WhatsApp or SMS broadcast with them; as long as they consent to being included for this sole purpose, you should be OK.
- Then repeat until backlog clears OR a big supply drop hits.
Yes i know it will take time on your side, but with communication and rules it should work and people would be happy. Stick a phone message on saying 'do not call about AMD 6xxxx series' and rotate a couple extra of the customer services team onto the task, it's not like you're going to get a 30ft container of 4,000 6xxx series GPU in one go (If you did, problem solved!).
If a manual order takes say 20 mins and someone spends 7hrs a day on it, that's 3 per hour or 21 orders per day. If you had 4 people, 84 orders per day. So, 1000 orders takes 12 days if you did it all in one go to lock those orders in. If you did it on volume of expected deliveries as they became due in, it would be spread out as and when. Get the bosses on it if you can't spare the frontline staff, make them earn their profit
A competitor literally did a similar thing today, on launch day. They asked for people to register interest via email without even publishing a price on their website, then called them and setup the order on their side so the customer just had to pay (took four hours to get confirmation from them). It's how I got my card after OCUK site fell over and then i got stuck not seeing the 6800 series in the search or menu - i literally had an OCUK one in my basket but got no further