The ST 2.0 change over and TT 2.0 conversions were 10 month jobs so it's not that Disney can't do this. Soarin 2.0 opened overnight.Even so, it still shows that Disney can move quickly when they want to.
As far as builds go, this is closest to Test Track (GOTG will have taken roughly 7-8 months given they started a lot of work with ToT still open)