What on earth is all the fuss about? - it's not as if it's a new idea. I believe many airlines in the UK have used it in the past - and in what way would the CAA object - one pilot is nominated as PIC, signs all the paperwork, the other is SIC and carries out the appropriate duties.
I would say go for it especially if it avoids having contract Captains for the summer - as for the "CRM" aspects, you are meant to be professional pilots for chrissake - perhaps being in the LHS for a summer will make you an even better co-pilot for the winter.
What's the difference between this and being taken over and being bumped down to the RHS as was the case with BA taking over BCAL or even within BA having turboprop Captains bidding into the RHS of the 744's. It meant frequently flying with a crew of 3 or even 4 Captains and I cannot recall ever having any "problems" on the Flight Deck. I can only think of one man who disliked not being a Captain that at the first opportunity bidded for turboprops in Scotland
Like I said before - go for it - any time in the LHS is better than none.