SBrittain - First post - Welcome to DealershipForum.
Concerning your core swap proposal, would a dealer need to send their extra core to your store and then have you send it back for credit or could they send it back on your behalf to the return center to save on shipping?
If a dealer needed to send the part to your store I'm guessing that shipping costs would limit the appeal of a core swap to dealers that are near one another. By contrast, if a dealer could return a core to the return center directly on your behalf it would make a core swap attractive to every dealer in the country.
Frankly, I don't know enough about the core return process to know if the second option is allowed by FCA.