You have some good ideas there, but it still bothers me that you are depending on the original wiring (it seems?) through the bulkhead connector for power in/ out of the interior.
High-amp current is the root of all evil with these connectors. Even "back in the day" I saw failures of these, including my own 70 440 sixpack which had an "optional" 60-65 A alternator, and "a little bit of amateur radio gear."
Long before there was Al Gore or the internet, I removed the main feed wires, drilled 'em out, and ran larger gauge wiring in/ out of the connector.