Thinking about the time travel aspect made me realize he could borrow elements from "inception"
The multi layers on layers could apply to time travel
-We have one time traveling team in the 70's( First level)
-One in the present for some contemporary action sequences(second level)
-Another in the future(third level)
Whatever someone does in the time periods(level) affects future events.
Maybe by the end of the movie the future we saw in the beginning has gone through several time changes
It's so far removed from the beginning that it's now considered an alternate reality.