Slowing down seems potentially dangerous to me.
If your catching up with the aircraft ahead of you then slow down, this is basic airmanship. How else do you avoid grinding the tail plane off the aircraft ahead or tail chasing them down the final approach. Obviously it will be dangerous to slow down below the aircrafts minimum safe speed. If the circuit is controlled by ATC then the controller will ensure safe separation including sometimes an orbit. Without ATC: orbiting, extending downwind or flying a larger pattern is precarious and should not be encouraged. .