The baggage-sorting and upgrade loop sounds easy to understand. Are you planning to make each terminal introduce a noticeably different challenge so the progression feels more than just faster sorting?
That's actually something I'm working on right now! I don't want later progression to just mean "more bags + faster belt." I'm testing different bag mechanics, shift-specific challenges, more active terminals, and other changes that force you to play differently as your career progresses. Really appreciate you bringing this up because that's exactly the direction I'm trying to take it!