It would stop a little bit of spam. I was thinking maybe a 5 second cool-down.
If you try to speak before 5 seconds it will say:
"You must wait for the 5 second cool-down"

 

I don't think a cooldown is needed. Also 5 seconds is very long so maybe it could be lowered to 2 seconds.

 

Doubt it would prevent spam. It's just the matter over an overabundance of players talking, and not enough mods online to kick said spammers.

 

No support, a lot of people would get angry.

 

Sorry, first of your ideas that I don't like.
Also just update your existing thread and bump it rather then creating a new one