Optional error level to use with WP_DEBUG

Hello.

tl;dr -> Allow PHP error reporting level (which WP_DEBUG would use) to be set in wp-config.php to suppress possible errors between wp-config.php and the after_setup_theme hook.

I have a feature request regarding WP_DEBUG and the level of errors that WordPress spits out when WP_DEBUG is enabled.

In newer PHP version E_STRICT has been merged with E_ALL, so WordPress begins to report E_STRICT errors too. During theme development this is great … until you install a 3rd party plugin with a bit outdated code.

The E_STRICT reports appear usually on each and every page, because plugins are not being loaded “according to strict standards”.

I’d rather keep theme related and plugin related strict standards notices separated. Because plugins are seemingly loaded before the after_setup_theme (the first hook available to hook into from functions.php) I cannot suppress plugin related errors in theme code (I tried various ways of setting the error_reporting value).

Setting the error level in wp-config.php does not work either, as WordPress resets the value in wp-includes/load.php. When WP gets to after_setup_theme the system has already possibly complained about numerous errors when loading non-theme specific contents.

Could an additional PHP constant be created to be used with WP_DEBUG (e.g. WP_DEBUG_LEVEL or similar). This constant would be optional and would default to whatever the current WP version uses. It should be able to be changed in wp-config.php.

Thanks.

EDIT: I know how to use mu-plugins, but I personally think this feature could be useful a core addition.