Gauges options: always, greyed or gone.

[Niwashi]

It's not shown initially because you have to switch to the Job for the first time after 4.0. After you switch, it then appears.

All that appears is a box with the name of the gauge. But in order to see the gauge itself, so that you can tell where it's really going to be placed, you have to have the status buff active. For some jobs, that's easy enough. For others, it's annoying to have to be in combat while adjusting your HUD Layout, and only get a brief chance at it then. (The only exception seems to be ACN/SCH/SUM. The Aetherflow gauge is always visible.)