The extras being added to the full loss part of a PCP is normal industry standard and usually dictated by the finance company process.
The way Morgan offer extras would seem to be unhelpful to the PCP process. From recent experience Mercedes and BMW offer few extras, rather they are bundled into packages, which then becomes part of the car product description on the V5A. For example "Premium Plus Package) and "Shadow Package". Perhaps MMC needs to look at the way others do this; perhaps a Sport Touring Package, which includes a range of no cost options.