So if you don't get into a lot of airports in the first few years, you can never get in as all gates at most worthwhile airports outside of your home country (where you cannot build terminals) are taken.
In reality, major international airports will add capacity when there is demand to bring flights, passengers, and dollars into the local economy. They wouldn't expand because one foreign carrier wanted one extra gate, but if there's a large amount of demand from lots of carriers, the airport authority would certainly look into expanding capacity.
So how about AE implement a feature where when an international airport runs out of gates, you can "request gate construction." When, say, five or ten gates' worth of construction is requested from a collection of airlines, then the gates get built. The requesting airlines would have to pay a premium for these gates, so let's say the charge should be 2x what an airline in that country would pay per-gate to build a terminal in that airport.
This keeps the game from being a race to block out every gate in the first few years, and keeps established airlines on their toes as others can expand into their international hubs.
What do you think?