Can incubation be slowed down just before hatch time?

I wouldn't want to risk it.

 

I wouldn't risk it either. They can start their pips and zips and be left in the bator for 48 hours or longer before really needing food and water.

I believe if it was an emergency I would have someone on call to check the bator and take care of chicks taken to the brooder box when the hatch was finished.

 

In theory yes, but you run the risk of more things going wrong and the chicks not hatching properly. You'd have more chance of the chicks hatching if you just left them alone. I had to leave on day 17 once and came back end of day 21. I stopped turning a half day early, raised the humidity, left instructions for someone to remove the vent plugs as needed and came home to find 3 chicks out and the rest pipped. Chicks don't need you there for hatch. Sometimes things go better when your not there to mess with them and they can survive days without food or water after hatching.