You can do it, you just don't want to. It'll be hell.
James Gunn kicked off a little storm on Facebook recently when he said that he finaled a shot after 749 versions.
Now, for people in my job, that has a particular meaning; that someone did a version, showed it, got told to change something, and then repeated that process over, and over, and over again.
Some clarification later seems to say that he was referring to 749 stages (multiple designs, tests, sims, animation blocking, renders, comps etc.) from the filming to delivery, but still, imagine that for 2000 shots.
18 months is fine if you start filming today, but to gear up, film and post a movie that fast; not a good idea.