Many worlds get filled to the brim with people and within a few years almost all gates are gone. This makes it really hard to expand and find gates abroad as you cannot build terminals out of your own country. My idea is that you can enter an 'agreement' with an airline in another country either already within your alliance or not and be share their terminal. The terminal owner should be able to control how many gates are leased out and for what price. There should be a terminal market where people can advertise publically or privately to specific airlines.
e.g. Delta Air Lines enters an agreement with KLM and shares the KLM terminal in Amsterdam and Delta terminal in New York.
^ I just made this up. idk if this is a real example.
I feel like this could be a reason to join an alliance other than just your rating and another reason to add codeshares.
Sorry if this has already been requested.