As for stage storage, while a hanger would be ideal, it would really only be needed for active reflight processing. "Idle" stages I speculate will be post-processed, possibly the major avionics removed, shrink wrapped in a manner similar to what they use for truck transport, and just parked outside until needed. Maybe an extra tarp staked into the ground for UV protection of the shrink wrap, and some desiccant canisters in the avionics bay.
Now, SpaceX may indeed need another hanger, the existing one for pre-launch prep work up and a new one for the post-processing work. Space-X won't need more than that though, I think. We have parked airplanes outside forever, rockets aren't THAT much different.