It occurred to me this morning that the game already has a framework that help make tanks aware of the need for tank-swapping and Provoke, before they get into an endgame instance:

Guildhests

From the very beginning, Guildhests were designed to be tutorial battles, to help introduce players to various mechanics commonly found in the game. The last Guildhest is a level 40 8-man party, which for many is their first introduction to playing the game as a Full Party (aside from the odd FATE party, where no Full Party synergy is needed).

SE could add another level 40 8-man instance. There might be trash mobs or whatever to keep the DPS and healers in the party engaged, but the main enemy would be a Medusa-style Lamia who does not auto-attack and has only two special attacks: An attack that petrifies the current enmity leader, and a Shatter attack that kills anyone who is petrified (and does pitiful damage otherwise), alternating on a 20-second timer. The Guildhest instructions would clearly spell out the need to pull the Lamia's attention away from the petrified tank, and possibly even suggest Provoke specifically as a useful tool for doing so.

Because it's a Guildhest, it would still be easy to win. If the tanks are unable to swap properly, healers have plenty of time to raise the dead tank, and even if both tanks are dead the Lamia would have plenty of DPS to petrify and kill, giving the healers plenty of time to get the tanks up. Still, it would introduce tanks to the idea of trading hate, a very common mechanic in later battles, and give tanks a chance to learn that Provoke is expected.