Your number 2) gave me an idea... how about having showflat and showthreaded check for the "post deleted" and if the body only consists of that, then why show it... have it skip that... as if it wasn't there...
If there's really a troublemaker spamming the board overnight, I'd still hate to see my board plastered with thoses posts even if they say "post deleted by Admin". I really prefer for Admin deleted posts to have the option to dissappear. Maybe both paths could be implemented, by giving Admin/Moderator the option to purge the post (or mark it in such a way that it won't be shown anymore, see my idea above) or just mark it deleted with the "post deleted by Admin" part.
