well, actually you COULD do what you want but then you'd have to throw away the rest of the segments and that would not be allowed. Since the ticket itself will have to be issued to show round the world travel you will end up with a bunch of extra flight coupons. Since a RTW is normally valid for a full year couldnt you use the rest for a later trip? The savings over a normal ticket on your routing would most likely be significant - esp. in J or F class.