Not sure if this is the right place, WordPress encourage the use of Child Themes and there is a movement in this direction.
One problem area is when you create a child theme and you do not want the "Custom Background" and "Custom Header" support, as the design of the theme relies on these being left as default.
There are functions to add theme support but not to remove theme support for all theme features.
Some are listed as "Extra Theme Support" but there is no function to remove support for these functions.
You can remove support for "Theme Functions":
-> Post Thumbnails
-> Navigation Menus
-> Post Formats
You cannot remove support for "Extra Theme Functions":
-> Custom Backgrounds
-> Custom Headers
-> Editor Style
-> Automatic Feed Links
The pages are added with the function add_theme_page(), but there is also no remove_theme_page().
Rather than having to create core functions for these, could the header and background support functions in the twenty ten "Default Theme" just be wrapped in a conditional function that can be overwritten in the child themes function.php