There is no good way to modify the default landing page.
Assuming 7.2.2, you could build a custom query that excludes your root aggregates based on their naming pattern, and sorts the remainder by the utilization metric you're most interested in. Build that query into a custom dashboard, and you're off. You can then bookmark the new dashboard, if you want, to bypass the default landing page.
The necessary custom query goodness is new in 7.2.x, so this fix won't work for older versions.
Hi Matthias, Jim is correct. In 7.2.2 you can utilize a Query to exclude AGGO's, and modifying the query to exclude the root aggregate takes only seconds to perform. The Query can then be used to define what the latest query Widgets display. Again, this ability only exisit in 7.2.2 and there are 5 new Query widget visualizations to choose from.