There is another possibility, though its remote. In NYC, there is an old subway station that is no longer in use. This station was taken, and turned into the NYC Transit Museum. Its still connected to live tracks. Granted, there are no out of service stations on BART. But, what would it take, both in amount of dollars, and besides dollars, to build a "station" either on a stub end, such as by Antioch, or Pleasanton, or even at Millbrae or SFO, or to cordon off a relatively small section of a yard at Daly City, Hayward, or Richmond to build a "station" and display a series of cars, perhaps 1 each of an A, B, C and C2 car, each restored to its original appearance, as well as whatever retired or soon to be retired MOW equipment their might be. Of course, it would be preferable for this to be under some sort of cover. This way, it could be connected to a 3rd rail, still connected to the network, and if BART ever decided to do what NYCTA in NYC or CTA in Chicago have done and periodically run a "history train" they could do it easily. For added history, in the advertising space on the cars, put up replica advertisements used from when the cars were first put in service. Nothing says a non profit couldn't be formed, such as what the Transit Museum in NYC is.

I know that BART is obviously no where near as old as what NYCTA or CTA are, but a start needs to be made somewhere.

Now, to get lit on fire, as I'm sure there are several on here who would like to crucify me for the idea...