but unforunately the nature of a market is often that it's not the informed minority that set the price, but the uninformed majority.
Sorry to sound so argumentative, but I think in the world of Caterham 7's it's CC who determine how easily sold, a 7 is. Because they won't buy anything that strays from standard it takes away a sizeable chunk of the buying market. This does affect how easy it is to sell a car but I'm not convinced that it has much affect on the price.
I think your idea to separate your upgrades into two parts makes a great deal of sense.
In your position I'd seek Mssrs Greenalds and Pitchers opinions on how best to proceed. Be prepared for some straight talking though, especially from Mr P 😬