Quick home electric question

The problem with your last plan is there may not be a lockout made that will fit that configuration You will simply have to do some research. if not, you could install a big transfer switch 'ahead' of the last box. It's for sure a gymnastics act between affordability, convenience, and legality and safety

Also consider the safety of the generator.........lots of thieves make off with gensets, and all they have to do is listen and watch. If you can afford some wire, you can move it