DL and UA have supposedly been in talks with Amex and Chase respectively about pre-selling a large block of miles for an attractive price. If the price is right, Amex/DL may offer a transfer bonus. I am not sure whether these usually come from the bank or from the airline or a combination of the two; obviously DL's motivation is to raise as much cash as possible from that relationship.
I think the concept of selling lifetime lounge memberships would also not be out of the question, probably for about $5,000 or so. One of the issues is that once someone has a lifetime membership, a lot of the ancillary revenue opportunities (annual membership, Amex Platinum card, Delta Reserve card) become tougher to sell to that person, which in terms of lifetime value for the customer are likely higher.
I would also expect to see some aggressive offers to buy MQMs/MQDs at the end of the year, or possibly to outright buy status. It's likely worth it to DL to to annoy the elites that earned it for a year to raise some cash and stay alive.
Offering a value-bonus or a bonus in miles for buying a gift card now would not be crazy either; there might have to be some limits so that you don't turn around and buy a flight with it right away though.
Gift cards are an interesting phenomena in my view. Back in the days, you would get a physical gift for somebody or you would give them cash. Cash would provide the flexibility to the recipient to decide what to buy. Then came gift cards ... I was thinking of you but couldn't decide what to get you and figure a gift card would be a great option. So, rather than giving you cash (or check), I'll limit your flexibility and give you a gift card. I have no idea whether you ever want to eat at xxx or buy something from yyy but you have the full flexibility to spend as you like. Sure, they may be instances where delivery of the gift card is easier since you can do it from the comfort of your home but in many instances, these are bought at supermarkets or stores and included in a physical envelope that is delivered in person. Why not settle for cash?
Now, on the topic of attaching a discount, they can certainly attached a validity period that is a day or some other time to address the purchase and use it instantaneously just to get the discount.