I'm not a civil engineer but I've never really understood the almost universal appeal of the GAL site. I mean, the amount of work to shoehorn a stadium into that small space seems to me to not be worth the effort and cost. You have a major highway, several streets and access roads (that will have to be moved), and a pile of train tracks (including a station) that will have to be dealt with. If I were an engineer, which again I'm not, I'd think that my first thought we be, "surely there's an easier place that's just some flat land we can build on."
To me Willets Point/Citi Field parking lot just seems like the most logical and easiest place to build a stadium. If it's the parking lot then construction could start tomorrow (not counting approvals, etc.) or if it's Willets Point then after the cleanup, which would be someone else's problem (maybe).
Never understood the love for the GAL site, other than that it's close to Yankee Stadium. And it doesn't seem the Yankees organization cares all that much about the team, despite owning 20%ish. So surely there's better locations for a stadium than on top of a railroad line.