This plugin will not help, trust me.
You can only reduce the chance that this can happen.
-nobots
-bot_quota 0
and important: bot_quota_mode not on "fill"
You can also try to set block suicide commands for humans too, so they not able to change team.
And after all you can try a combination with this two:
Genrerate a fake nav without laggin the server:
https://forums.alliedmods.net/showthread.php?p=2069582
Blocks the download of nav files for clients:
https://forums.alliedmods.net/showthread.php?p=2069582