I’m afraid I still don’t really get the point you are trying to make.
My understanding is that you have said that the 414 has an altimeter that shows either inHg or hPa depending on the unit settings. It sounds like that is already working as intended and is a part of a 3rd party add-on.
This thread is a wish-list item for the sim itself about expanding the units settings to be more configurable rather than the current system of just metric / U.S. / hybrid as those still result in incorrect units being shown in the sim’s UI.
I’m not sure how this wish-list item applies to use use case you have described (altimeters in 3rd party addons supporting both units of measurement).
I’m not sure if maybe you are also requesting that the unit settings also apply to all aircraft instruments so for example the ASI can be configured to show in knots, mph, km/hr etc but if that is the case I think I disagree. The aircraft are usually modelled off real life ones and the instruments and the units they use are generally chosen specifically to match.
Please let me know if I am missing something or have misunderstood.