The problem is if you want to have all lights
in house and possibillity of using all plugs,in this case you need many circuits to put on
subpanel(plus fridge,subpump,furnace etc).
The easiest way is to install main
disconnecter after meter and transfer switch
(service rated) and connect generator. Customer knows that generator is not big enough for all house(full calculated load) and will take control of load. Generator is protected of overload so that I can't see a problem for this solution.
If customer is not at home in case of blackout generator is big enough for load
remain switched on.