With far more taxiways, gates, and parking spots, the new IST will be able to land almost twice the aircraft per hour while still allowing aircraft to take off at the rate of the old IST.
A 3rd runway is needed. But parallel runways have a huge advantage over crossing runways. The taxiway system will really help too.
On a totally different note, but somehow similar.... I have been hooked on this game called "airportCEO", where you start from scratch and build bus-stops arriving from the city, terminal, checkin desk, security lines, gates, boarding gates, jet stands, runways, taxiways, staff rooms, bathrooms, shops....Most of the scheduling of the airlines could be done automatically... it is more of an architecture, flow of passengers and aircraft type of simulation.
After 40 hours or so of play, I have 3 runways, 13 Medium Gates, 9 Small Gates, 16 General Aviation stands, bunch of shops and stuff and making money regularly.
It is a steep learning curve. I suggest to watch some instructional youtube videos before jumping in, especially from youtuber, "ConflictNerd".
It is fun and gives you a small glimpse of large scale airport operations