You need to talk to a pro from a fireplace shop to really make sure what you want is feasible . IMO only if you are removing the FP from the kitchen since someone else buying the house will not know what you have done inside that system. Some pics too would be helpful and also the age of the house.

Thanks. It's not a functional fireplace at all, because there's an HVAC duct that runs from the crawlspace up to the firebox. We will seal that at the crawlspace end. The firebox hole will get a clearly removable "lid" so that no one ever mistakes it for a functional firebox. 1958 house. Here's a picture of the kitchen fireplace.

Diagram of the fireplace wall. Light grey is the firebox, orange is the kitchen chimney joining the living room chimney.