How to adjust the customize.php page in admin without editing the customize page?

I have multisite running and I am not allowing site admins to change themes and want to limit many of the items they can adjust. Specifically, I am using the SimpleMarket them and would like them to be able to adjust most of the appearance. However, I would like to hide the "Static Front Page" and the "Widgets: Sidebar" options from the accordion menu. How can I do this with editing any of the core admin files?