I've been working on meters and gauges for many years (my gig was instrumentation and process control). Unless it was boogered with , I don't remember your concern ever being a problem. The face is screwed to the movement and then it's usually screwed to the housing. Vehicle gauges are some of the toughest around due to the vibration they experience. Accuracy is another matter.
If this is keeping you up at night I might try increasing the post holes in the back of the case. You could then slip an insulator of your choice over the post (tubing?). Then run an extra nut with a insulating washer (fish paper) below it down to the the insulator, the wire lug and lastly, your capture nut. . This is of course boogering with (see above).

Six volt guy living in a twelve volt world