As I've told others all the rulesets have diverged on ct_host/ct_client so this is ONLY for 5E. But yes I don't see it as a herculean task to modify it for other ones. I know someone else told me they were going to make personal mods for 4E or something. Wished them luck. I just don't use anything but 5E - if at some point there is enough interest I can probably try to learn how to do those but this is just out of the gate and need to see how it goes. After all the primary customer it has to satisfy is ME. As that is who I wrote it for. Personally I can't live without it in my session prep now but as I only do 5E that is my priority.
You can't escape cluttering one map with a ton of tokens - especially if the LOS is complex. However, LOS is going to apply to the active token so not really seen any problems in my stuff - but then I'm more about having lots of group icons on my global map with the non PC group tokens all invisible to the players - then have each of the groups in their own personal maps which when the PC group encounters I just drag them into it - seconds to set it up instead of all the pain of pre setup. Now do I have thing with multiple floors in one map where there is a ton of NPCs in? Sure. But again a lot of that can be your memory/cpu on your machine - nothing will save a weak machine. Though this can help drop the load since most code only processes what is visible in CT - that is not true for everything. Example being it takes me about 10 seconds in my current COS campaign to bring up my 250 CT entry 10 map bonanza I have going. But I abuse it. Terribly. And understand that I will pay a price if I stick to much in there.
Anyway - let me know how it goes.