There is no doubt that Plymouth will close this year as a licensed civil airport with SHH handing in their licence back to the Belgrano for revocation. That is a legal/paperwork exercise which leaves the facilities intact (unless the CAA employ a demolition expert)
Operations that require the use of a licensed aerodrome do not include military flying. PPL flying training can now be conducted at unlicensed aerodromes too.
Maybe there's a compromise where the north west corner of the aerodrome could be retained and the rest sacrificed on the alter of development?
SGC