For sure there are inline boosters which need phantom power for themselves and do not pass through it to the mic. Maybe even simple 'blockers' exist…?
Anyway it’s a good idea from rexet in my opinion. An accidentally switched phantom button can happen and I guess such a security pop up wouldn’t be that hard to implement.

I think even then, there is a good chance that you accidentally choose the wrong option.

Besides that, there are a lot of different use cases and scenarios where it wouldn't fit and make operation only much harder.

#1 Does it need a questionnaire after each power-on or after recalling one of the stores setups?
     Maybe the setup was changed in between or the device moved to a different location.

#2 What about stand-alone mode without TM FX?

#3 What about setups with many preamps / microphones in combination with #1 and #2?

I agree it would be handy like the OP. But on the other hand nothing is worse then a false sense of security in this case. Only thing that would work from RME side IMHO is a switch at the underside or backside that disables 48V and even that only works if you are the only user.
The only foolproof solution for valuable mics is a blocker or a selfmade cable (pretty easy to make) and even then you will have to think about not forgetting them.

Regarding SW, it could be done, that one could configure particular input that 48V switch may be disabled and enabled. Say, point mouse on button, rightclick and choose from local menu enabled/disabled.

If disabled, one could not change state of button. It would be on or off. To change the state of button one would have to unlock its state to enabled.

I agree that still better is to use HW blocker or mic that does not mind.... But improving SW a bit may help as well....