Bidline has two failings:
1. If there is no movement in seniority, it can be a bit harsh on the juniors.
2. It is complex, so a lot of people, especially those outside the company and new guys don't understand it.
As regards number one, I still think it is better than an allocated or Carmen system - those rostering systems are worse for choice, even if you are junior.
As regards 2, if the company/BALPA taught people a bit more about it, then the learning curve wouldn't be so steep. However, once you have learnt it, it outshines the rest by a long way.
There cannot be any fiddling in the main process - the only scope for fiddling is with overtime outside the bid process, but if you DON'T want extra work you don't really mind who gets it and the fiddling is only possible if you want overtime.