This is what I was using, Departures on Level 1, direct access from Boarding Desk to the Jetway. Arriving passengers went from the Jetway down the stairs to Arrivals on level 0. This was an A35 build so some of the save files aren’t loading under B1.1
It all worked, up to the point where the whole area between the Gates and Baggage pick-up was a mass of PAX with red speech bubbles wanting to eat at the Departures cafe and use the upstairs toilets. Similarly, the Departing PAX were wandering around with their legs crossed wanting to use the Arrivals toilets.
The main issue is the PAX not being satisfied with the facilities provided on the Level they are on. They have a ‘whole world’ knowledge where they should only have knowledge what they can currently see. They shouldn’t be looking through floors to find a destination, they should be restricted to access to areas on their current zone (as in Check-in, Security, Departure Lounge and Gates, or Arrivals area and Baggage Claim) and recalculate when they (have to) change floors or zones to see what they can access there.