Well the TransAsia ATR crash highlights the danger of a crash of a much larger plane into Taipei city buildings. Such as the A330 , which currently is the largest plane flying into and out of Taipei.
Taoyuan seems the obvious choice, but some are saying the 3rd runway in Taoyuan is needed before it can accomodate the SungShan flyer numbers.
Someone said relocate to TAmshui? Where in Tamshui would be suitable for an airport?
Only thing I can think of is an OFFSHORE ARTIFICIAL ISLAND built off Tamshui such as Chep Lap Kok of Hong Kong and Osaka’s new Kansai airport. An MRT connection from that would be an easy way into and out of Taipei city. But the idea of Checking IN at SungShan is dumb. Just make SungShan into a large park like Central Park of NYC. But please not more and more buildings on that piece of land. The area around it can already be then redeveloped into high rises.