How to inhibit observers as choice of sides?

How can the “observer” choice in the selection of sides be eliminated or at least inhibited?

What I’m trying to accomplish is to have a hidden OOB that no one can see until they choose a playing side; therefore, allowing observers to see the pieces is undesirable. My objective is to make a hidden OOB that only becomes visible to the player(s) of that side. All others, including the observer would not see it.

I realize that the “observer” is used to create the scenario.vsav so that the players will see the side selection choices.

I’m hoping there is a trick, something like editing the module to then remove the observer from the list menu. When I need to edit the module again, I’ll add it back to the list. Or if there is a “developer” property that can be set that adds “developer” to the list of sides.

I too am looking for this kind of functionality. I don’t want my players to be able to see others pieces or terrain before the time is right.