This thread is a great argument for a National Seniority List. You get hired at your first Part 121 carrier, you get a National Seniority Number. Then mergers/acquisitions would be strictly DoH.

Sure, Part 135 and military guys are going to get hosed, but they're not Part 121 airline pilots so its a moot point.

Additionally, you get furloughed or you're airline fails, you should get a preferred interview based on your NSN.