Instead of finding ways to comply with these absurd laws, I'd really love to see these manufacturers follow Ronnie Barrett's lead and just forsake Kalifornia all together.
If normal everyday folk can't own a particular weapon, then refuse to sell to agencies of the law as well (including repair/replacement parts).
In the words of the Anthony Hopkins character Col. Ludlow, "Screw 'em!!!"
When the "gang bangers" are still armed and supplied and the cops are hamstrung and can't get crap to work with, maybe they will open their eyes to the situation of the regular law abiding citizens of that state.
And yes, I know this would also hurt good folks who want firearms, but then this could be the impetus to DO SOMETHING (but I doubt it). They have sat on their thumbs for forty years and allowed this to happen. Almost every other state is working to allow better arming of it's citizens and CA wants to be like England.