BuddyPress.org

Another approach would be, in your header, wrap the main menu links with this code:

switch_to_blog( 1 )

...your main menu links...

restore_current_blog();

Also check out this plugin, http://wpmudev.org/project/New-Blog-Defaults, it has a bunch of handy options for new blogs. Including setting a default blog theme.

In BP there are more ways to skin a cat Thanks for sharing your solutions.