bandwidth consumption

I need to be able to control site users' bandwidth and diskspace usage.

At this point we are primarily concerned with bandwidth.
I thought I'd get some feedback on how I'm thinking about solving this issue:

• Create a module for Aegir that requires Apache module mod_cband (http://codee.pl/cband.html).
• Module provides a settings panel per site that allows for bandwidth limits to be set.
• Module implements hook_provision_apache_vhost_config which generates vhost config for each site that reflects the bandwidth settings.

And advanced features:

One of my low-traffic sites was hit with significant trackback spam. We found out when we were notified by our hosting provider of a significant bandwidth overage for the month.

The spam module was doing a great job of keeping the spam out, but due to the flood of trackback requests during a sustained period, we experienced a massive increase in traffic.

I have now disabled trackbacks on that site (ti's the only site I had set up to allow trackbacks) and have enabled the spam module's "Trackback Black Hole" module so that all trackback requests are dropped immediately.