What's so complicated?

"We’re buying each other a gift this year to keep undelivered in the gift box in addition to our normal purchases."

2022  buy $10K for self, and $10K for gift for spouse.  Do not deliver gift.

"If the interest rate is still good next year, we’ll buy normally and keep the gift in the gift box. "

2023  if rate is high, buy $10K for self.  Still hold 2002 gift don't deliver.

"If the interest rate isn’t good anymore, we’ll skip the purchase, deliver the gift, 

20XX  if rate is low, don't buy $10K for self.  Just deliver 2022 gift to spouse.   

"and cash out immediately."

20XX  since rate is low this year, once your spouse receives the gift, she cashs out.