What is the function of Simulation Mode?

Hint 1 of 4:

By entering Simulation Mode, you can enter a simulation of the future to see
what effects the Plan for Renewed National Purpose will
have on the world.  Specifically, Rockvil.

Hint 2 of 4:

Keep in mind that, in Simulation Mode, you will reassume the identity of
Perry Simm.

Hint 3 of 4:

Simulation Mode was designed to test whether or not the Plan was a good idea.

Hint 4 of 4:

It also serves another function very late in the game.  (Don't read any
further if you haven't finished part III.)