Since voting is not allowed, an In game console app for clan members to kick players. In a large clan you can't give everyone full rcon access and sometimes admins are not on the server but a clan member might be.
There is a php based rcon tool that can be accessed through the steam internet browser that allows you to do rcon in game. It is customizable for individual users, and you can set up privilages for each user.. so you can give each member a username/password, and kick, but not ban or whatever privilege set you like...
I didn't write this bit of code, but I do use it. A very nice tool if you can't or don't want to give out full rcon. You just set it up on your web server, and away you go. Not too difficult to configure either. I finally found a use for that free webspace that Gameservers gives you with a server.
There is also a integrated rcon tool that another team has in development that I've heard will be something like the integrated rcon tool for cod2... if you remember that far back.