Fullwings,
That's all well and good in theory, but why would anybody in their right mind entrust an aircraft and it's occupants to a very junior (maybe less than 1000hr) FO when there is a multi-thousand hour captain sitting beside him? There is no amount of initial training that will raise the FO's standard to anywhere near that of the experience of the captain, who would have many many more rejects in the SIM, as well as seen many many more takeoffs, eg birds flying across in front and therefore is in a far better position to decide what to do
and to execute the subsequent manoeuvre correctly.
"Sharing the workload" at V1 minus 5 is a furphy. Action must be taken immediately, and that should be done by the captain. V1 is
the one time things have to be got right, and as I am responsible for the aircraft, then I want to be the one that makes the decision and do the stop.
What might be a long-term problem is (as a company) treating your first officers as lower forms of life who are incapable of making important decisions or handling the aircraft properly.
Only an egotistical maniac would, as an FO, consider themselves a "lower form of life" when starting out life in the right hand seat; just the sort of person who should not be making go-stop decisions.
When they eventually become a captain, where will all the reasoning and skills miraculously come from? One day not worthy, the next standing in judgement...
All the other training stuff, SIM exposure and exposure to line ops will prepare the FO for the left hand seat. Haven't you ever noticed, over the course of a couple of years, how FOs develop from a green-behind-the-ears novice who stays "close to the centreline" to a skilled, capable, assertive crewmember who is prepared and experienced enough to go to the limits and who would easily slip into the left hand seat?