Re: 4 player multi-player - what's stopping you from brining six players in that circumstance? You'd have the same problem.
First of all? Game engine ... to allow party of 4 players bring two companions with them (wich is allready implemented fully, just require adjustment in value "maxpartymembers" from 4 to 6) that is not a problem ... But if you would like to add two additional players, you would need to rework whole engine.
In the words of the senior NCO instructor at cadet battalion: “If you ain’t cheating you ain’t trying. And if you got caught you didn’t try hard enough!”