Delta has 100 options for A320neo. That means a price has already been set. No need to play games like you suggest. If Delta wants to retire the 717 early in 2025 then an agreement must be reached with Boeing Capital. That's why the Max is a wildcard. Either a deal must be made or Delta will be paying leases on retired 717's sitting in storage.
In the current COVID World, only the OEM's and their strategic partners are offering finance on new aircraft deals. Add the word MAX to the equation, and 100% certainty Boeing Capital will be financing, lease or purchase.
For DL, a low cost MAX deal, that provides a plane which can be used and abused with no financial penalty on shorter routes, has multiple exit points, and removes 717 commitments at the same time would be attractive, if they see the need, and can handle the internal PR.
An Airbus deferral deal on existing orders may specifically preclude other purchases without penalty, which DL would likely want Boeing to absorb.