Plutonium

You can host BO2 on Linux, I know because I did it myself (I think on Debian?). Not sure about MW3 though

Menu is quite buggy if you're not the first person in the lobby, I have a few members join and suddenly the menu gets all jank and skipping options in the menu, you press F to confirm the option, and it does something totally unexpected.

Personally, I'm looking for a way of interacting with players for administrative purposes.

Seems like there isn't too much in that department.

pickle-nick as long as you load it using the official method (not injecting) no you're fine

Roachhh
Yes it work but is better to look at this with the ne Plutonium Version
https://forum.plutonium.pw/topic/3147/how-to-set-ranks-with-id