Dear Rabbi, When serving soup on Shabbat, is it permissible to ladle the soup directly from a pot which is on the blech/electric warmer or must the pot be removed first?

Better not, as there is a difference if the soup is liquified completely when it may be permissible, and if there are blends and there is a problem of Magis. It's better not to ladel directly from the pot when it's on the blech.