Chosen Solution

Can an SSD be placed in place of the Airport card?

The system was not designed for that and it won’t work.

No, you cannot use an SSD to replace the AirPort Extreme card in your 2014 Mac mini. Although, OWC offers “data doubler” kits to add a second HDD or SSD to a Mac mini, they do not currently offer a kit for the 2014 model.