We can agree to a Hong Kong style of control for San Diego. I doubt the Californistanis would give a damn about keeping Fort Irwin and extending that to be a part of AZ or NV--not that we'd need to keep NTC. You wouldn't believe how much open space we have at Fort Bliss, TX, for doing the exact same mission. Would the Marines care about losing 29 Stumps? Doubtful, but, again there's lots of room other places for them that are probably not as crappy.
I say let 'em leave.
Last time this issue came up the Union made a big deal about a pile of rock and brick in the Cooper River. That cost us 600,000 dead. Are we to make that mistake again?
What about three or four small states?
Southern CA from OC to the border could be conservative. LA county and environs can be a liberal state. Make Jefferson higher up and east including a lot of central. And a Bay Area state around SF and Silicon valley..