Optional Stylesheet Enabled by Default

I'm trying to create an intermediary base theme between Omega and the sub-themes that I'm creating. So it will look something like this Alpha-Omega > Intermediary Base Theme > My Sub Theme

The problem I seem to be running into is that the stylesheet from the intermediary theme is showing up under the Optional Stylesheets section as disabled. I'd like to force that to be enabled by default when I turn on my sub-themes.

How do I accomplish this?