The guy who's standing in there should at least get a nice chair to sit in.
Now, since he's not in a relationship or appears to have feelings for any of the girls involved, we can't call it a cuck chair. But maybe just a spectating chair. (Though to note, I am just skimming through and not reading half of what's written so maybe I just missed something. Plus I've rapidly just tossed out any visual indication of emotion from the faces depicted since everyone seems to have a permanent blush on their faces except the MC.)
Also, Oyakodon and Shimaidon guaranteed, and he can have the orgy while also piloting the giant robot that is also himself. Man's living multiple dreams at once, good for him.