I agree that certain more technology is required for paratroopers. For example, flight with advanced infrantry tactics.
I mean, Michiel De Ruyter, the great admiral of the Dutch Navy in the seventeenth century, invented marines
since he thought it might be of strategic importance that rapid deployment of troops could bring victory. The concept worked. His seasoldiers (as the marines were called in those days) were important for vicories in the wars between several countries and for the colonization. The ship bombarded the target and the seasoldiers captured the structure. (or whatever)
So Yanks, again someone else had your concept earlier. (this time even BEFORE the United States were born
)
Now serious again, THREE centuries (paratroopers were not used in action before WWII) between marines and paratroopers, that is way too much. I say (as above) that paratroopers can be built after flight AND advanced infrantry tactics have been invented. This would also be a bonus for the civs with lots of knowledge, tactical important units should be obtained after more inventions have been made.
Regards,
Bartemans
http://home.hccnet.nl/stolte.1