Total damage caused by the use of accessories

I would like to know whether you can suffer an economic total damage due to insured accessories. Let’s assume that a vehicle has a market value of 3000€ (without modifications). On this is a (accessories)wheelset in the (new) value of 2000€. The insurance does not provide a new for old tee. The accessory wheelset has been insured against additional fee. Now the wheelset is stolen, the insurance commissions a reviewer who comes to the following: WBW 3000€ residual value 2000€ gschäden 2000€ Then the VN would get 1000€ – SB and its vehicle would be considered as total damage?! In itself, the invoice is actually clear, if the vehicle would have been equipped with standard wheels. However, the (comparable) vehicles available on the market do not have such a wheel set at all. Is the actual damage with the difference between WWW and residual value collected with it and if so, how can one be insured against this risk?