I too don't follow your logic all that good about not using the shore power cable. Your generator will require a qualified cable going from the generator to the trailer from the truck anyway - might as well use the provided shore power cable. Then you can turn breakers on and off for the appliances you want to run from each generator or shore power source.
My generator sits secured in the tailgate area of my closed and lockable truck bed. I pull it out on the tailgate when I need to use it. I plug in the shore power cable using a RV30A-15A adapter. This works out great for my OFF-ROAD POPUP setup.
![](http://i.imgur.com/YZMuX.jpg)
Your setup of course is different than mine... You can install a MANUAL OPERATED 120VAC SELECTOR SWITCH beside the Power Distribution Panel to select which 120VAC circuits you want to use for each of the two sources. This idea would work great when using a high wattage INVERTER as a 120VAC power source as well...
Lots of work and will require pulling out romex cables and rerouting wiring...
These photos from google search shows some of this.
![](http://i897.photobucket.com/albums/ac177/unyalli/PowerDistribution3cropped_zps2b3a88c3.jpg)
![](http://i897.photobucket.com/albums/ac177/unyalli/PowerDistribution1cropped_zps508f5fc3.jpg)
The switches come with several stacks of switches (BLUE SEA) Three are shown here...
![](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSZwnKLA_KRQZwu36mB3Wy7LZfg7ikb682CinUuJMU7v96dqsak)
All 120VAC wiring has to be installed in qualified Electrical Boxes like shown here...
![](http://i1081.photobucket.com/albums/j357/shooted11/TransferSwitchIns008.jpg?t=1332984183)
![](http://i47.tinypic.com/2mgrqq0.jpg)
![](https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcTwtRAQ0lUQk0IrQjDOx_QFCabvExQDXKpTaxmXAjcBsXaMusordg)
Food for thought - Please follow Standard Electical codes for your mods mainly for those who gets the trailer after you. Got to be safe... The law suits come after something bad happens...
Roy Ken