I think you need to take this car for what it is and what its claiming to be, it's listed as a Modified 3.0 CS, don't think anybody will bid for this expecting to get a CSL.
I'm doing a rep CSL build because it's a dream car for me and I would never be able to afford to buy one finished and ready for the road so I bought a rusty, none runner, auto CS 10 years ago. I have spent money on repair panels for all the normal places and took the front wings off, glass out etc, and carried out a full respray, repaired all the wood, all work done my myself. I've got a Bat kit for it, 5 speed box, triple webers, correct radiator, Frits bits headers, W&N stainless exhaust, Scheels, recovered rear seats, Coupeking wheels, Petri etc.
Spent a lot of my time and money doing this as a labour of love and hobby and by spreading the cost over time it's been affordable for me but I would not like to know how much I've spent so far, not just on the CSL specific bits but on all the other bits needed to restore an e9 properly.
Would I get my money back if I sold it, don't care really as the plan is not to sell it and if it gets sold after I've gone at least there will be something to show for it.
I don't think there's anything wrong in changing a car to how you want it, just be honest about what it is.
Finding faults regarding this car not having everything a real CSL should have is easy but not everybody wants to go that far or are that bothered. I love a 100% correct car, all nice with polished nuts and bolts underneath but also enjoy other peoples pride and joy that might not be anywhere near top standard but is still loved by the owner.
My car would never be mistaken for a real BAT, it's a right hand drive for one thing, which suits me fine living in the UK.
That rear bumper just needs levelling up.