Sure, (plz note this is just an idea and that I don't know if Innersloth will actually be doing something like this or not(this is just the way I think this should go)) I will answer each of you questions as follows
Story: Story would be something like the crewmates are dispatched into the far reaches of the galaxy to find a planet suitable for live. On the way from MIRA HQ (a base above Earth) in the SKELD they come across multiple planets and space stuff (all of them visable from the telescope in the POLUS map) They travel from space until them find a Semi suitable planet, POLUS. They proceed to build a base there. While on POLUS, one of the crewmates goes missing, only to reappear a few days later. As the crew stays at POLUS, more weird things begin happening i.e. more disappearances, suspicious clues to the fact that this planet has other life forms as well. The Crew then splits in two, one half staying on POLUS to operate the base, and the other to fly back to Earth to get more materials, supplies etc. The Imposters (as their are more than one of them now) split up and go with each part of the crew. 1 imposter stays on POLUS and two other go with the remaining crew to the SKELD. Next, you play on the POLUS map. It's kind of like the Public servers from here. You play different levels in the story. Polus, which helps you find out about the imposters. Skeld, where the crewmates on the ship find out about the existance of the imposters from the POLUS crew. And Finally, MIRA HQ, where you play trying to track down the final imposter before he escapes down to earth. All of these are just ideas.
Played: IDK, I haven't really given it much thought.