I certainly understand what you're saying. Do I agree with it? No. But it is a reality that they will not negotiate on currently - just like the 28 day rosters.
And no, I disagree - it will NOT be like Jetstar or Qantas - I've previously worked for an airline with a TEN YEAR pay ladder, like Virgin's proposed four year pay ladder. The difference with Virgin Blue is they're introducing it NOW, not when they started nearly ten years ago. When I started flying before, there was no jealousy or anyone upset - it was just an acknowledgement that there were crew on tenth year wages and I started on level 1. Just like the acknowledgement of nearly every airline out there regarding seniority. I had the opportunity to do the time like them to accrue to their level.
Virgin's 4 year pay level won't take too long for the crew to accrue to our level (compared to 10 years for example in my last employment). At least its not like Jetstar or Qantas where we potentially have crew on different agreements period.
As I said I worked with an agreement exactly like this (except 6 years longer) and not once was it brought up during a flight. Its a shame they want to save money this way, but at least they're not outsourcing and therefore effecting us altogether. eg: calling them out on availables instead of us.
With my personal experience, I would say there would be NO complications with crew among a flight. It wasn't even talked about!