Thank you for sharing your thoughts about the StyleSheetManagerProxy class.
Your implementation will suffice in cases one needs to add embedded style sheets in a Content page or a UserControl. The other would be to directly add the settings programmatically to the StyleSheetManager's StyleSheet collection.
Currently we do not have plans for adding such a control to the suite, still we will reconsider your suggestion in the future.
All the best,
the Telerik team