The absolute "Seniority is the end all and be all" position of BASSA is simply outmoded and Mixed Fleet is specifically designed to cure that problem.
I recall quite well 20 years ago sitting across the table from counsel for the opposing side, asked for, and giving my position, and this gentleman saying "I've been doing this for 30 years and I'm not ready to listen to the likes of you".
My response was "I could care less if you have been doing it for 1 year, 5 years, or 500 years, if you've been doing it wrong you don't get a cookie for term of service".
Mixed Fleet, as a customer, is rather interesting. From a SLF point of view imagining a Fleet totally committed to its promotion and renumeration based upon customer satisfaction is a rather engaging ideal.
I'll be looking for the hats.