Can't help you with the screwy California gun laws, but I had heard what you said about some of the dumb laws not applied to rimfire. As always, the folks at CalGuns.net are your friends.
 
I've been surprised that Kel-Tec hasn't introduced the SU-22C sooner. It seems like a simple modification, and the 15-round mags have been available from Black Dog for several months. I guess everyone at Kel-Tec has a lot on their plates, meeting the huge demand for their older product lines, ramping up RFB production, and rolling out the PMR-30.
 
I was on the Bud's Gun Shop website yesterday and I noticed they had two versions of the SU-22. One had an 18" barrel but little other info and no picture. I wondered if this was a new model from Kel-Tec, or a Bud's error in their inventory database. Wouldn't be the first time. Still, two different barrel lengths, two different prices...
 
http://www.budsgunshop.com/catalog/advanced_search_result.php?keywords=su-22& ;x=0&y=0
 

I got an answer from the calguns.net forum.
OAL, the total length of the rifle would be under 26 inches (with folded stock), and that is illegal in CA.  Here is the answer to my question from someone on the calguns.net forums:
http://www.calguns.net/calgunforum/showthread.php?p=4445894&posted=1#post444 5894
 
So, if I put a muzzle break and lock tight it on permanently to get it to 26 inches, that'd be legal.  I'll keep it in mind.

It says on the very last post that the law only applies to centerfire rifles NOT rimfire. You can have pretty much anything you want on a rimfire rifle in CA, just not on an "big bad and evil" centerfire rifle.