I cannot see how, technically, you can do that. You want to show the accounts CPU or memory usage over time based on a percentage of overall usage on the server? Considering nearly all accounts are likely to be a fraction of a percentage of overall usage, it would seem a moot point. Indeed, percentage of cpu time is a silly measurement, since any process will use as much %age of usable CPU at any given time. The problem is that you don't have anything to measure aganst.
One of the main problems is that the WHM report, from a performance perspective, is pretty much meaningless.
You're much better off protecting your server with resource limits for individual processes using both the "Shell fork bomb protection" and, if you have particular problems, /etc/security/limits.conf
