I think it would help if you can join higher server but not a server lower than your Threat. For example a Bronze can join Bronze, Silver and Gold Servers (like if ppl in a clan want to do an event), a Silver can join Silver and Golder Servers but not Bronze and a Gold can only join Gold servers. Another Problem in my oppinion is that you get the Silver/Gold WAY TO EASY play a mission get 1 kil die 10 times gratz your silver now and so on.
But meh who am i to judge.