Originally Posted by frau kaleun

The Merchant Fleet Mod is set up to do something like this... it has a great number of ships that are modeled to be "neutral" in appearance, but which have their .cfg files added to the rosters of Allied nations (as well as neutral ones). So a ship may have, for instance, no flag flying from any masthead, but wear a skin that identifies it as a ship from a neutral country. But if it spawned in that instance from an Allied roster, it will behave like an Allied ship and the game will count it as an enemy kill if you sink it.

That's different than what happens if you sink a "suspicious" ship that spawned from a neutral roster, though - it might seem to be heading for an Allied port but if the game spawned it as a neutral and you sink it you'll take whatever renown hit comes with it, unless you've edited the basic.cfg to remove the hit for neutrals. You can even change it so you get credit for sinking a neutral.

Then it's all up to you to exercise the necessary self-control so that you're not just sinking everything you find in order to get more renown for spurious kills.

I don't know how to go about making an enemy ship run with its lights on, and I don't think doing it would be very realistic anyway... all that would do in RL is make them more visible to the enemy, easier to spot and track and easier to ID once they came to investigate.