The idea of controlling multiple characters at once in a game has existed for a long time, yet no one ever seems to find a good way of implementing it. You managed to solve the problem flawlessly by turning it into more of a strategy game. Being able to pause and direct the ghosts allows you to control all of them at once, all the time, without ever having to sacrifice accuracy or reaction time. For example, if you say had 16 buttons on the keyboard, or 4 joysticks to control the ghosts, it would be a nightmare to coordinate them, and the best most people could do is focus one at a time, but your system allows you to coordinate all 4 at the same time perfectly.
Great game J&T