From my understanding, one can at least make the police stainer randomly remove the lightbar by adding lines or changing lines in the vehicles.meta file. Does anybody know what the changes are, where to add them specifically, and if they work with any police vehicle, not just the stainer?

Remove FLAG_EXTRAS_REQUIRE from the Flags line.

The default vehicles other than the Stainer don't have lightbars as extras, and don't have misc lights that would look good without roof lights anyways. Modded vehicle models might, and you can change the same thing if you use those.

Thanks