Kirkhill,
Your unusually fertile mind has produced a lonely little onion in a petunia patch - to fiddle with a song we both may remember from our youth. (For the rest of you, there was a post-1945 ditty that began "I'm a lonely, little petunia in an onion patch . . .")
First, the FOO is the fire support coordinator and provider for the combat team. His/her job is to get the vehicle in the best position to do that. The FOO party must also be able to operate dismounted supporting a ground attack, climb on a helicopter or man a ground OP well separated from the vehicle for protracted periods. The vehicle also requires specialized communications and other gear which would eat into the ammunition space in the MGS. None of these features are generally thought to be good things by our black bereted friends.
Second, no one is suggesting, I hope, that the MGS would operate in others than multiples; single vehicles are a no no. While having more than one FOO would raise the social tone in the combat team no end, again this is a non-starter.
p.s. I have kept the tone light not to ridicule your proposal, but to gently point out the unusual breakdown in your thinking.