The first one: If your car is on fire and you are able to stop and get out, and then you feel like using the mandatory on board fire extinguisher, where would you like that to be? Bolted to the floor of the passenger side (where everyone puts it) so that you have to reach back into the burning car you just jumped out of? No, that's stupid. How about just inside the door where all you have to do is pull a quick pin.
The second great idea: You know how everybody installs the window net into a hole on one end, and a seat belt latch on the other? That pretty much is impossible to do by the driver once he's strapped in isn't it? What if one end was attached by a heim joint? Then the net can still drop out of the way, but it's always attached, and all you have to do is swing it up.