but selling an Amex with "premium zone 3 boarding" doesn't have the same ring as zone 1
While AmEx may advertise Zone 1 boarding, as soon as the AmEx card holder lines up, he/she finds out it is the third to board. Other than the first time this happens, the CC holder then knows "Zone 1" ain't the first zone! Make Zone 1 the F cabin; Zone 2 DMs, PMs, and GMs; Zone 3 FOs (yeah, me!), the AmEx holders, etc. I really doubt AmEx holders will get rid of their cards just because they have to wait as they do now anyway for Zone 1. AmEx could rationalize this with something like: "board right after First Class and SkyTeam elites".