Well, basically it is a load of bolleaux.
If you have been in the right seat of a 747 (or similar) for xx years, then the obvious move is to the left seat of the 747 (or similar) for you are well up to date with the job in hand and are not likely to cost the company very much money.
Why would you want to go back to puddle-jumpers for xx years just so that the company seniority/union plan says so?
I left the RAF (Transport Command) in 1978 and joined Fred Laker as an F/O on the DC-10.
One year later I moved straight across the cockpit (I could have gone on the BAC-111, B707 or A300) but I stayed on the DC-10 and have never regreted it.
Every time an airline finds it difficult to keep the troops happy, they will undoubtedly find a new "seven labours of Hercules" to stabilise an unsustainable situation.
You are either capable of being a long haul commander or you are quite simply not.
In either event, you should at least be allowed to bid for the job.