Not sure how easy/hard this would be to do, but this would be REALLY useful. When players disconnect, there's a reason for it. endofstream/quitting, whatever. I am staff on a PvP server, and I really would like a plugin to check the last 5 disconnects and their reasons. This would help for checking for combat loggers/xrayers/etc who 'disconnected' in the middle of whatever. Not sure how easy/possible this is, but it would be REALLY nice.
I agree this would be useful. I would assume it should be fairly simple to make, but I'm not a plugin developer, so... idk. I often have to check my server console to see why someone quit, which requires switching my screen over to my server computer.
You could try "Combat Tag" as an anti Combat logger option. but it punishes people who disconnect legitimately.