I just wanted to make a comment regarding getting a powerplay even if you score on a delayed penalty.
I think if you score on a delayed penalty while your goalie is still on the ice, then you should get a powerplay because it was still a five-on-five goal. If your goalie had left the ice and you have an extra skater, then it truely was a six-on-five goal and no powerplay should be awarded.
That would mean the refs would have to keep track of where the goalie is, though, which might be too much for them to handle.