It would have to be a VERY good deal for me to support randomly getting 20+ C-17s, given all the other shortfalls. If if they were free it still represents a massive investment in infrastructure (even if they're parked), and personnel (to some degree even if they're parked).
A lot of these discussions completely ignore opportunity cost. Money and people don't grow on trees. 20 C-17s means something else is getting dropped.

