Is there a way to keep people off of your server that don't have the same mods installed as are installed on your server? When Antares goes down repeatedly I'll switch over to my own personal server. I've had a few problems with people joining and having incompatible mods, crashing the server, so I was wondering if there was a way to mod-check and kick people that don't have compatible mods.
Not an official way, no. We do however handle these things retroactively. We log server errors and trace them back to problem users.
You can potentially look into third party asset digest modifications as far as your own server is concerned.