This was actually my very first Oblivion mod REQ way back when. I'd want the PC to go into the seductive idle (I think it's MS04SeductiveIdleA) after standing still for a couple of seconds. Nothing else. Have no idea how to do it, although I know my way around the CS. Any help would be appreciated.

You need to add an entry to http://cs.elderscrolls.com/constwiki/index.php/Idle_Animations and set proper conditions for it.