Within another division of the business you're referring to LHLisa, the cabin crew have a very similar system to the 737 pilots - rolling seniority. The difference is the seniority numbers aren't published & you don't know where you stand officially - however you can generally tell with your bidding power from one full year's roster where you were more successful in gaining desired days off over others.
So each crew member has two seniority numbers, a static and a rolling. The static is used for staff travel, redundancy & LSL purposes, and the rolling is used for roster builds only. While this division don't have the power to bid for specific trips ect it works very well with day off allocations ect.
I guess at the end of the day, unless you're #1 seniority you will never receive a perfect roster.