Broadband,
Thanks for your comments. In several airlines around the world -EK to name but one - they have a rotating bidding system for flights, days off etc. It works very well as it is fair to all. That is, you work your way up the ladder month after month, and when you get to #2 or #1 slot, you get basically what you ask for, keeping in mind that in a month or two after that, you will be down the bottom again.
The original question I asked was if this had been proposed to KA or CX Rostering Departments before.