1)Is it possible to have multiple BSPs in a multiplayer map?

2)Do timers sync in multiplayer?

3)Exactly how much do device machines sync? What are their limitations, and at what point do they get out of sync?

It is possible to have multiple BSPs in multiplayer, any .scenario file can have BSPs, for the BSP switch timer sync, it would maybe have to be like the Device machine sync script, but instead of opening and closing doors, changing and changing BSPs...

My idea was a map where every few minutes you have to find the safe spots on a map while it transitions to a new setting. The first level would be a laboratory, and then it would go through a cycle of tilesets, like desert, tropic, grassy, snowing, blackened, and such. Then it would return to the lab after so many minutes and repeat the cycle. Each safe area would be a bunker or a tunnel, or a beam of energy. There would also be time warnings and such.

What happens when you don't make it in time and the BSP switches on you?

you die. that or you start in the same spot but on the other BSP, meaning you could be very high in the air or under the map. The safe areas are in the same place relative to the other safe areas in other BSPs. This does not necessarily mean they are in the same place relative to the map; they are in the same place relative to the frame.