This suggestion is for something not on current cameras. A manual locked exposure setting that selects the correct ISO for shutter speed. So controls would be shutter speed and scene brightness in EV100 scale: https://en.wikipedia.org/wiki/Exposure_value#Tabulated_exposure_values
Examples of EV100 levels:
15 Direct sun
13 Cloudy bright
6 Home interior
etc…
Switching to this mode could use the current metered ISO/Shutter/Aperture to set the starting locked EV100 value for scene brightness, after that raising shutter speed would raise ISO to maintain the same EV100 value, changing the EV100 value up (brighter scene) would lower the ISO (and lowering EV would raise ISO). This could work with adjustable aperture too although most phones lack that. EV100 would stay constant while ISO was used to compensate for either shutter or aperture changing and would maintain constant scene brightness.
The annoying part about the current Manual/Auto ISO approach is that recomposing causes exposure to shift because the meter is constantly in use for the auto ISO. The alternative of setting ISO manually is annoying because you have to adjust the ISO every time you adjust shutter speed or aperture if you want to maintain scene brightness. AE lock is close but not repeatable whereas EV100 level is a standard.
ISO doesn’t represent photographic intent, it’s a side effect. Intent is Shutter speed (motion control) Aperture (depth of field) and EV (scene brightness).