If I only have one type of light, I see no reason to waste my time learning the others. Since the shotgun is so limited in use (and likelihood of being there when needed) I see no reason to own one, much less spend the time and money to train with it. At typical home defense ranges, the pattern is 3-4" wide, so it's really no help at hitting anything, anyway.
Look, I know you make your money teaching people, but I learned all this stuff while you were still in kindergarten. I"m 60, and I knew Jeff Cooper pretty well already in 1973. I"m worked with Farnum, Ayoob, Wilson, Dalton, Hack and many others. I am a firm believer in KISS, so i'm not about to split up my training with a shotgun that feels and operates a lot differently than my rifle.
Nosler Partition softpoint 223's are FINE manstoppers, guy. Shoot some critters with them and you'll see that they are every bit as likely to stop a man as a charge of buckshot is. Buckshot doesn't get the "Mach II effect" of having the temporary gas cavity being able to destroy fragile organs. Note that I did NOT say muscle. The only muscle inside of the chest cavity is the heart. The lungs are nothing more than airsacks, the spleen and liver are so fragile that they can be damaged by a bare knuckled punch. The kidneys are so shock-prone that I once put a guy on one knee with a little flat foot round house that I barely felt touch him. :-)
I've been hurt far worse (and hurt people far worse) while sparring than I've seen guys hurt after a fight that had gone on for many seconds! I've had 2 ribs broken in two places by a single up toes roundhouse kick, by a novice, no less. i've have my lips spread all over my face by an elbow (again from a novice).
the fact is that the very great majority of the time, IF you get the gun NOTICED by the bg IN TIME and if you are smart enough to leave him an escape route, he will take it. Many of those who don't flee at just the sight of the gun will have their minds changed by MISSES, too. :-) This fact is born out by cases printed by the NRA EVERY MONTH in their "armed citizen" columns. If this were not true, there'd be nobody buying mini-revolvers, derringers, .25's, .32's, etc. Cause those things are nothing BUT bluff.
I shot IPSC for 4 years, and out of the hundreds of guys I saw compete (and I do mean at US nat'ls and world shoots, not 10% impressed me as being able to adequately dominate an attack scene. I've known quite a few spec ops types, too. Most of them impressed me even less, actually. As a guy who trains them once told me". Shooters they are, gunmen they are NOT". :-)