This may be kind of stupid, but if someone made a mod that allows two people to sit on a couch, would you get it, if only for cosmetic reasons?
It should be easy enough. You'd just create two couch items, each using the image of half of a couch. Then place them right next to each other. The OKEA kiosk has a bunk bed that does this same thing.
I think I would use it on my server, I always had wished two players could sit on the bench in Vanilla, when I first ran across one in a Forest Biome, I immediately yelled at my buddy, "DUDE THERES A BIG CHAIR WE CAN SIT ON!!!!" Even had him come all the way to me, and nope EDIT: pitched the idea onto my server "Hey guys, want a mod that lets 2 people sit on a couch, etc..." Immediately spammed back with "zomg YES" It's funny, as simple of an idea as it is, it sparks interest.
Welp, it took me longer than expected, but I did it. Seating positions are still a little wonky, but hope you guys can get some use out of it! http://community.playstarbound.com/index.php?resources/two-person-couch.1892/