Senior pilot is a relative term, but it isn't someone trying to avoid reserve. You shouldn't expect to hold weekends off at that relative seniority. The "contractual right" to 4 days off was voted out, and the majority apparently decided that it wasn't worth holding on to. So, it is now your contractual right to waive it. Everyone is playing by the same rules. You could try to make the same argument about any of the waivers usurping seniority, but it just doesn't hold water, it's in the contract the majority voted in. In 6 months the argument will likely be moot. If you don't like it, tell your reps, or ask your scheduling committee for more 3-day trips. Ultimately, who gets to decide if the 4-day waiver sticks? That decision was also waived to the JPWG in this contract.