I have my own plans for chat, slightly different to what you suggested.
- Mods will be able to temp-ban anyone for either 20 or 60 minutes.
- All users will be able to 'vote' to kick users. If 5 users kick a user, they get banned for 20 minutes.
- Some kind of week long or permanent ban for multiple offenders.
- Possibly a way to IP-ban users from chat to avoid multiple accounts.