If I was on the committee to accept the proposed uses of the hanger I would have serious doubts about the viability of this project.
The "rain or shine" argument is not so much of a selling point in Southern California. It rains so little there that an open field track wouldn't lose that many days.
On the flip side of the coin, it doesn't look like you would get the benefit of the sunshine. The hanger walls look to be rather opaque, I would suspect that it would be rather dark inside even on a bright sunny day. This would mean that you would need lights, lots of lights. The electric bill could be staggering.
I am not sure that I would want to ride in a totally wind free environment. It would be essential that you kept the dirt moist or the dust would be a major problem.
I doubt that the retail outlets in the building would fare well. During a major event they could get a lot of interest, but during the week they would suffer. A fitness center that is more than a few minutes from the home or office would not be very popular. A restaurant????
That artists conception is WAY too bling! Come on, a raging waterfall? Even if the land an building were obtained for free the cost of constructing even a scaled down version of what you have proposed would be staggering. You sure wouldn't recover that investment collecting from a handful of riders a day. What the artists conception lacks are grandstands, which is where you could make some money by hosting some major MX/Supercross type events.
What would you anticipate would be the cost to ride at this place? How many days of the week would it be open? What hours?
If you want us to support your idea then share with us the data you have to back it up. By this I mean the cost to build your layout, the operating cost (this includes insurance, which I am sure would be a lot, electrical, water, payroll, etc). Then tell me how many riders a day you would need to break even.