Derin as you know Im a bit of a BMW fan myself having owned a few in the past inc an E30 318i to an E36 M3 Evo Cab. If in the future I was after an interesting BMW that was immaculate, I'm sure I could buy it from you with my eyes closed, literally! In fact I would rather buy a used BMW from you than BMW themselves!
ps I would suggest getting emblems made e.g "Derrin" or "D Spec" etc for the cars when they are sold, well a bit like Alpina/ Brabus/Pinafarina! It may catch on, you never know, enthusiasts would know it is a mint/concours BMW & not just any 528i