Unusually I am going to have to disagree with Beags on this issue.
There is absolutely no reason why pilots should not be trained to operate in both seats (IMHO on all RAF multi-engined types). There are the usual arguments of "it would be too confusing for the poor little darlings" which can be countered with " they know no different so will except what ever they are taught as abos". If the sims were set up so that the course crew pilots (a captain and a co) alternated between seats then they would accept that as the norm. This would then mean that when a co was deemed ready for captaincy he would just be given captain status. No dramas, no need for a co-captain course, no extra costs!
The additional benefits are if you are short of co-pilots you have captains who can fly together from either seat. As long as one is the nominated captain for the trip then again no dramas (except the argument over who is going to carry the nav bag). Indeed on Beags old Sqn they went through a period of retraining captains in the RHS to act as cos because of an extreme shortage of that type of beast.
Despite Beags anti Mighty Hunter comments the fact is that both pilots on an OCU course would probably be abo first tourists. Both flew from either seat (except for T/O and landing and below 1000' AMSL if my fading memory serves correct, but stand to be corrected, when the QFI would occupy a seat) and both learned how to do all the trick flying ie DEFATO, flapless etc.
The system works on maritime and has done for 30+ years so there is no reason, IMHO, that it could not work elsewhere. Perhaps only the old shiny 10 mentality that still pervades 2 Gp is the only problem!