Sorry to bring up an old thread, but I missed this earlier and since I design facilities, I'm definitely interested in this topic, but here's my take:
At least for audio, the mix position is ideally out in the audience so they can hear what the audience hears rather than being isolated in a booth. Many times, both the lighting and audio are out in the
house. This isn't always feasible, but when it is it makes little sense to have the SM by themselves in the booth (although the SMs may like that idea). Having the SM out in the audience is usually not a good idea as calling cues and call lights are very distracting to the audience, some of whom may have paid to see the performance on stage rather than the SM's performance. If you have monitors for cameras, clocks,
etc., the potential distractions for the audience get even greater.
The SM usually needs space to lay out scripts, notes, cue sheets, etc. It's nice for them to have some dedicated space and finding sufficient room in an often already crowded booth or
FOH can be difficult. And you try to talk an Owner or Architect into pulling out seats so you can provide space for the SM at FOH instead of their being on stage.
This may not be applicable with qualified stage crew and ASMs, but those can't be assumed to exist in all cases. In many school or community theatres the SM takes great responsibility for the crew
safety. During a performance the lighting and sound board operators probably aren't going to do anything that's safety related beyond maybe falling off their chair. Not so on the stage. So it seems to makes sense to have the SM where they can most directly prevent or react to any situations.
So I often incorporate a dedicated tech position or additional comms and 'god mic' connectivity at FOH so that tech rehearsals can have the SM, LD, etc. out in the house, but this is not used during dress rehearsals or performances. SM position is usually on stage, typically downstage right, sometimes with a dedicated movable
desk, with the comms main station at that location. A remote comms station or secondary connections for a comms station are in the booth for an ASM or alternative SM location. This seems to be a fairly standard configuration