Did Colt SAA, or the like not have a safety notch/pin located on the cylinder face in the same manner as cap and ball revolvers like the 1851 Colt Navy? If they did have that I don't see what the issue with having all six chambers loaded as some how you would have to cock the hammer back, then have it land on the hammer. Which in that case an empty chamber wouldn't help either.
No, SAA don't have any kind of safety notch or pin like some of the percussion revolvers did.
What they DO have is a 1/4 cock position on the hammer. This keeps the firing pin from resting directly on the primer .
Problem is that a sharp blow to the hammer (like being dropped on it for example) will break this "safety" causing the firing pin to hit the primer hard enough for it to fire.
With the hammer fully forward the firing pin DOES rest on the primer. A good solid hit to the hammer will fire the gun.
With an empty under the hammer, the only way to make it go off is to cock the hammer all the way back so as to line up the next chamber.