Custom scenarios: How to detect if a given player is a bot or a human?

I'm making a map where the ai would literally find it impossible to play, but the map can theoretically be played single player; however, to function the game does require that all player slots are filled. With this in mind I'd like to be able to:

In the case of multiple human players: simply remove the ai players.

In the case of a single human player: put the bots in a position where they can't interfere with the human player in any way, and also make them immune to the loss conditions

I seem to remember seeing this done once, but it was long enough ago they I can't say for certain that this is what I saw or what map it was done on.

So, to content creators: Is it possible to do this? And if so: how?