I always wondered if this would be possible.

The only problem is how to get the lights to appear for neutral/night time/single ships only. If that could be done, we could designate certain skins for certain nations and thus have correct neutral flags and shipping companies as well. :hmm:
The best thing I can think of would be to clone each ship and have one version for belligerants and one for neutrals. Of course, then there is the matter of neutrals like the US entering the war at a later date...
I am sure someone more experienced will come up with something.