grammar - Must a coordinating clause always have a subject?

E.g.,

(1) You are getting yourselves into a very dangerous situation; get out of there at once.

The imperative following the first clause has an implied subject, so would this mean it is a coordinating clause? If the above sentence was coordinated with so, would that change the status of the clause?

(2) You should wear a suit, a clean shirt and a tie for the interview, and be punctual.

Is and be punctual a coordinating clause?

(3) Worcester is a very sought after porcelain, and is regarded as the finest of the period by many experts.

The following clause of this sentence contains a passive structure with an implied subject, so does this make it a full coordinating clause? How would the status of the sentence change if by many experts were omitted?