There's actually a very simple solution to this. A built in trigger lock. Not meant to replace the mechanical safety catch already built in to all modern guns.
It's really quite simple, and is foolproof. A built in mechanical lock that only opens with a fingerprint scan and password. So you pick up a gun to use for the day, and unlock it. Now it's ready to use, Whenever you want. It automatically relocks itself after 12 hours, unless it's a police or military weapon which is settable to never relock itself or after some custom time period. If it fails to unlock, then you have time to fiddle with it while in a non-attack situation, or take it in to a shop/tech to make it work. If the electronics fail the mechanical lock opens.
So, if you're the type of person who keeps one around for self defense, you can unlock it when you come home, or before going to bed, or before going out for the day, etc. Or make sure you always keep one unlocked, etc. 100% access, even if it may not be 100% reliability at any given time.
That's just one example solution to the "complexity"/"reliability" argument. I own a gun. I have children. My gun(s) are secured. In order to kill me with my own guns and take them, you'd have to first load it, and then unlock it. Which means you'd need to get the keys(s) from me first. It's not a perfect-foolproof solution. But I also know hand-to-hand combat. I've had people try to rob me before. Ms. Lanza was negligent in her care of her weapons, and should not have been allowed to own guns, until proving she would be responsible with them. I'm a big believer in the 2nd amendment. But I'm an even bigger believer in personal responsibility.
While talking of personal responsibilty. Why should gun makers be held responsible for acts commited wirth guns they made? Do we arrst and sue car manufacturers for selling cars to people who go out and kill people with them? Well, we probably do, but manufacturers are immune from those lawsuits. As they should be. The whole idea to allows lawsuits against gun-makers is a dishonest trick to sneak in the back-door of gun-control under the guise of manufacturer responsibility. Not that I am against "gun control". Guns in America are a right, but with rights come responsibility. If one can prove responsible enough they should be allowed guns. I'm not a fan of assault weapons, or of assault weapons bans. Assault weapons are only good for one thing. Killing lots of people, or other animals or plants. In fact I once saw Mythbusters kill a tree with a gun. Well maybe the tree was already dead. Hard to tell, it looked like a desert tree.