They would build a campus like Apple's new campus I presume. $5billion, 14,200 employees, 175 acres, 2.8 million sq ft.
I don't even know what a 50,000 employee campus would look like and where it would fit. Imperial's Quarry Park Campus is 3,000 employees, 20 acres, 850,000 sq ft. The whole West Village including roads is like 65 acres. Forget Firepark, you'd have to line 'em up nuts to butts to get 50,000 people in that area.
The Pentagon is 6.5 million sq ft, 26,000 employees.