A little less frightening of a solution:
add_filter('bp_template_include_theme_compat', function() {
echo template('page');
return '';
});
I personally use singular, but page should work out of the box for Sage. Unless you are using add_theme_support('buddypress')– BuddyPress just tries to override the_content() in anyway it can, so a generic page view should work as intended.