Mike,
You are right about the interior light. However, my Escapade has the interior light and when I used ot use the trailer, I had to wait in the morning a couple of times for someone with jumper cables to start my Wing, because the light got left on.
That is why we have the extensive Electrical Bay with Battery, relays, etc so that if you leave the light, air compressor, laptop, cooker or what ever else on in the trailer, it will not affect the bike at all.
Both the male and female connectors are availabe at auto parts stores and Walmart.
If you want the schematic for an isolation and battery system, eMail me.