The UV map contains information that isn’t easily accessible in the 3D model. If the UV map is good, then it should be possible to use for masking during sculpt. Particularly imported models, where you don’t have a zero-pose.
Simply have an extra viewport: The usual one with the 3D model and an extra one with a simple rotatable, zoomable UV map of the model, where you can use the same masking and face set tools.
Bonus for those who need to texture paint intricate models. They could use that view too.
Substance Painter does this, and it does it quite well.
I discussed it a couple of days ago with some blender.chat fellows on how to do difficult masks on models with lots of curled up geometry, like a character with a clenched fist, where you want to do some particular, corrective sculpting.
It probably should be separate from the UV editor, as the UV editor is focused on UDIMs, and has a bunch of editing functions, and also works only during Edit Mode.