those military weapons are all sub machine guns, small, lightweight guns ...
You have obviously never held a Tommygun. It is lightweight, only when compared to a crew served weapon! And several of the other early SMG designs are also in the 8lb+ range.
Modern designs, using alloys and plastics are much lighter.
I don't follow the chain of thought that says your best option is a shotgun loaded with 00. I am fighting to protect my property and family, why would I want a gun that fires multiple projectiles at once in multiple directions and destroy my own stuff and possibly a loved one?
it is difficult to determine sarcasm in text without a note identifying it, or using the little emoticons...
If its not sarcasm, describing a shotgun as "firing in multiple directions" really makes one wonder if you know what you are talking about. Shot loads do spread with distance, but at typical defensive ranges inside a house, not much larger than your fist. Now, if your house is huge, and you are shooting from one end of your olympic size pool to the other, then it will open up a lot more.
Pistol caliber carbines don't get that much respect because they are carbines. And except for the tiny fraction that are legal short barrel rifles, they are the same size as a carbine firing a rifle round.
Because of this, they have all of the drawbacks of a rifle (carbine size) and none of the advantages, (power range).
In the same size package one can get a .223 and with varmint bullets, actually less penetrative of walls than a lot of handgun bullets.
Rifle caliber carbines have their downsides as well, especially compared to handguns in close quarters. There's no free lunch.