Boeing apparently has been using all sorts of shortcuts in it's production lines, though so far it appears to have been limited to specific models.
One reason to slow down production is if the parking lot is getting full, hence why they need to deliver the planes that have been completed. I don't know about the rules of the road in the States, but I wonder if they're allowed to fly anywhere, say a storage area, if the the MAXes aren't certified.
The economics of airlines are fragile, and you can't employ an aeroplane whose model range statistically will crash every two or three years, even if you got them free. Well, maybe Aeroflot.