why not make this question a bit more general: why live with previous owners poor descision?
if a mod was done right, i'd be fine with it. if the car didn't come with an option i like and it can be retrofit to factory standards, why not? i would pay extra for manual over an automatic, even if it was changed later on in the car's life, if done properly. why live with dirty farted on cloth seats if you can install a nice leather interior with heated power seats? you get my point, i don't care as much about the window sticker reflecting an old car 100%... modifications might drop the value to the collector's that love pure originality, but there is plenty more people on the market that don't care as much.