Basic idea is excellent and well worth pursueing!
Only thing I can think of, off-hand, relates to your comment regarding "Of couse there will be owners saying the site may be miles from home" - using my home locale as an example (sorry!!) then siting such a museum in a place where I could realistically get to it to perform the maintenance required on the vehicle of my dreams and home again the same day would not be suitable for anyone north of Birmingham - and thats pushing the envelope.
Ideally you'd be looking at at least two or more locales - say North, South East, South west for starters.