A couple years ago I bought a Shad tankbag and decided to modify it with homebrew aluminum plate, pass-through 12v supply cable, and a triplet 12v distribution socket assembly hidden in one side.
Use a RAM universal tablet mount to hold my 7" tablet used for GPS navigation.
One thing I really like about this configuration, is that when I want to walk into a restaurant, or stay overnight somewhere, all I have to do is disconnect that one 12v supply cable from my accessory socket in panel D, and take the whole tankbag in with me. All electronic connections etc remain intact, AND are securely with me away from the bike.
After riding through thousands of miles in heat and rain, hasn't presented any problems.