Currently, QuickForm doesn't seem to support date/time drop-downs for non-default date/time elements (like %E, %m, %H, etc.).
As we allow the users to set these in the config, we should support them in the drop-downs.
My gut feeling is that it's simply a matter of fixing/extending the switch statement in HTML_QuickForm_date::_createElements().
I'd much rather we have this fixed in CiviCRM 2.1. Assigning to Michał, as my plate is a bit full at the moment.