Well, in a sense such a mod can only be well implemented in FAF since there is an opportunity to change the lobby.
In my vision of such a feature, loading a multiplayer save is done in the lobby, like choosing a map. (and you can then reassign players or do other stuff) So no opportunities for cheating there. To say that there's "no way" to make it unabusable, is a pretty big cop out.
Besides, I'm not particularly calling for it to be implemented as a priority (i said "one day") just an acknowledgement that its a necessary feature for a "perfect" FAF
So yeah, the kind of dismissive (and honestly, slightly ignorant) counter arguments I've been seeing here are the things I will fight. You can shut me up by saying, "Hey! That's a great idea! I'd love to do it one day! Yeah!"