This is going to be a controversial suggestion.
I think CM should ditch any kind of lighting system due to the high pop that it handles. Make it so that every tile is lightup automatically. BYOND doesn't let clientside players handle lighting (like most multiplayer games do) and it puts a burden on the server to run the calculations for every player. Lighting itself for this game is quite pointless. You can already see xeno sprites moving in darkness and the armor and rail flashlights already lightup most of the view. The only thing that lighting really effects is sniper guns but boilers already glow so again this is a moot point.
Shouldn't be too hard to implement and a trial run to see how much this affects lag would be interesting. I think most players would be willing to sacrifice this feature so that the game runs a lot smoother.