If something did happen in a darkened theater, he would have had plenty of time to take his weapon and chamber a round. It's not like walking down a dark street or something.
So you are suggesting someone chambers a round to walk down the street, unchambers to enter the theater (remember the terrorist in the Russian theater few months back?), and rechambers when they get back on the street, unchambers to enter the restraunt, etc.
If your method of carrying unchambered is the best way, why don't the cops use it?
What's the difference tween carrying a semi chambered (bad) but a revolver chambered (good). Many semis are DAO and have a trigger pull weight similar to revolvers. Should the revolvers be unchambered?
I think the NRA guidelines not to carry chambered and the restrictions against carrying shotguns chambered are primarily designed for hunting or field applications. Not self defense situations.
Can you chamber a semi one handed while pulling your wife or kid to safety with the other? (I know, you don't have wife/kids, wouldn't let them walk in dangerous places if you did.
good luck...