I feel an interesting enhancement to the game would be to introduce private and government contracts for the transportation of people.
I believe this could work in two ways:
Large contracts are put out for tender for specific country ie USA airlines in the USA are given a deadline to submit their price to the contractor. Now at this point ti would not rely merely on who is the best looking financially deal, it would consider the airlines CI, their route network, aircraft availability and the airlines financial situation. With this I believe airlines could be challenged to price ie in a two year contract to ferry workers daily at a set time to arrive for a set time they would have to in their bidding for the contract consider future fuel prices and their own airlines demands.
I also believe for smaller and newer airlines their should be one off or short term contracts such as ferrying 10 or so people between Houston and smaller out lying oil fields.This would be based solely on who is offering the best aircraft and price ie an executive of a business would not fly on economy seating. This could be a good cash cow at the start and int he future and give a use for the pesky small jets in the game.