I see what you mean.
My wife isn't incredibly gun savy, but she knows how they operate. She wouldn't be comfortable with clearing a double feed, but to point and shoot she does fine.
I cede the point of familiarity. Perhaps I'm assuming other folks carry more point and shoot style guns, and that's a mistake on my part. My wife and I have talked about what to do if she is uncomfortable with a gun... set it on the ground. If she was to use my 92 and wasnt sure about decocking, I think she would set it on the ground and step back.
I still think needing to carry the same gun is a bit far down the rabbit hole. The odds of needing interchangability seem low to me. The odds of needing familiarity are much higher - just from a non critical incident, having a gun in the house stand point.
Because my wife doesn't carry, I feel like I'm dragging this off topic. I'll keep reading with interest, but likely have little else to offer.
-Cory