My one problem with this is the assumption that the time traveling HAD to come after getting an exo body, I mean couldn't you make time travel, time travel to a time you could get an exo body- and then time travel some more. Or am I missing some detail that would render it impossible for one individual to use a different body then resume time traveling as they did as a human (aka is time traveling tied to the body or a transferable device? Because you did mention different people using the timeline device)