Reading through all of this, I think your best course of action would be to have a the purchase value for the stock bike when new, and have all your receipts or at least values of modifications (parts + labor). I'm sure if your bike is totaled, your insurance company will account for depreciation of everything, but at least you won't have to argue the validity or desirability of the mods you've chosen. If you can line item each mod (description, price, labor) and get your insurer to attach the list as an exhibit or rider to your contract, all the better.