Gaining an advantage by Violating?

[Time2Ref]

I had an interesting discussion with a customer concerning a game that he attended. I looked up the rule, but was concerned with the penalty. Here is the sitch:

A1 inbounding spot throw-in at the end-line. B1 closely defending the end-line. A1 steps back about 2 feet to gain some room to throw-in. A1 gets the ball inbounds to A2. B1 goes out of bounds and guards A1 so that A1 is having problems getting inbounds. No violation called.

Best I could find would be a violation on B1 for leaving the court. The penalty seems to be throw-in for A.

It didn't effect this game, but I could think of situations where B might gain an unfair advantage by continuing to violate. (Say they were ahead by 1 with 15 seconds on the clock. Team A wanted to call the play where the A1 throws-in to A2, comes inbounds, A2 passes to A1 and A1 scores. Team B is stopping A1 from getting inbounds. A1 is the best scorer on his/her team. B keeps violating, clock runs down. Penalty is still just another throw-in)

Is there a warning? Or just more throw-ins? Could delay of game be called after the first violation?

Any thoughts?