The time it takes for you to rack that slide is enough for someone to get the jump on you and end your life.
Really? Then with a chambered gun, the time it takes to raise the sights will also be too slow. Or the BG would be close enough to turn your loaded AND chambered pistol on you And you'll be dead. If the BG is close enough that you don't have enough time to rack your slide, you're probably screwed anyway.
If you keep your doors locked and hear someone breaking in you'll have more than enough time to rack a slide. If you don't have time then the BG is too close and you'd probably be better suited with a knife anyway. We're talking about a fraction of a second here, and I know in panic situations that counts, but really, if you're cutting it that close where you can't chamber a round before the BG reaches you, then other parts of your home security are flawed and a gun wont be of much help.
What you are suggesting is that someone should leave a loaded chambered pistol, with the safety off, within reach of their bed, to be safe from a BG. Any other configuration would "take too long" as you stated before, you wouldn't have enough time to rack the slide. And with a time space so narrow, the BG would probably be within arms reach of your loaded gun, if you didn't hear him break in and don't have time to rack the slide.