To be honest there is nothing you can do unless there is an admin or you manually mute someone.
On saying that maybe make it easier to find people by having different filter settings.
1. Currently Active
2. Most active
3. Players with Mic
5. etc There can be many different filter settings that can be added.
Having 5 or more people mute someone which then leads to auto mute can be bad. Also, it can depend on the number of people playing you could have 150 players having only 5 people mute you for a whole round seems very low as well.
1. People can be mean and just get friends together to mute people or just randomly get muted by players.
2. If there is an officer leading people and someone else wants to lead but no one follows him they can get people together to auto mute.
3. Some people just like to play without people shouting in there ear and thus mute them.
Limiting the speech of officers again I would disagree here as they will be leading people (Like I like to do).
1. If something unexpected happens and the officer now cannot speak it prevents him from leading men because he went over the limit seems a bit silly.
2. There is only one voice option for the officer so you would handicap the guy meant to be talking which would lead to other classes talking and taking command since they would not be limited.
An idea would be to have two voice settings for an officer a orders voice (current) and a normal voice (Everyone else) so if an officer (or captain) is talking to individuals not everyone could hear them.