it will probably be an option like on the 45 where you can have either an air conditioner or apu or neither. if you don't have an apu then you are expected to start an engine to power everything including the air conditioner (if installed). from a maintenance standpoint its a huge cost savings (in the 45), not only from not having to work on the apu but also because you don't have that big bulky thing sitting above baggage so a lot of things are easier access for maintenance thus taking less time. there are several 40/45 customers that I know of that have gone with neither and just start up an engine to cool the cabin down. although they typically go through more emer batteries because they always want to power avionics before they start-up. i've only really seen around 2 air conditioners installed on a 45.