The comparison I am making is between keeping it 'original' as is, with a genuine but old roof, albeit new window,
or
having a brand new aftermarket roof and window.
I believe the second will add value if you wanted to sell, the first could mean a buyer trying to reduce the price saying it could do with a new roof.
There is also a difference between keeping it original in the condition it is, and keeping it original with brand new parts.
Keeping it original would not lessen the value if you want to spend £4k on a brand new genuine BMW roof.
but would you spend that on a car unless it was worth £25k?
The issue is that non-m cars, and sadly even more so the smaller engine'd variants are no longer worth big money.
Aged originality probably means diddly squat in upping the value, versus brand new aftermaket.
Other opinions are available
