CURIOUS....if the engine is already away from it and he has access to the entire inside of the bell housing...why does he have to remove the trans?.... everything he needs to get at is already exposed.
The ONLY reason I can see that YOU MIGHT want to remove it is when you torque everything back in...it may be a lil difficult to keep the trans in a fixed position while torquin it down...that is a lil easier on a stand...but it can be done in place just as well...just takes a lil more time to bind everything up so it does not move