The "Nerv" Engine is actually called the NERVA nuclear rocket engine that was developed in Los Alamos Scientific Laboratory in the United States. Search it up.
Well the only benefit is not only using the only nuclear engine we got. The game already has alot of gas engines, so it's safe to say to add another one in so people can have a variety to choose from. As for a new nuclear powerful engine, the nuclear engines that Ive discoved is the ones from history, and Im pretty sure the developers don't want to add a made up engine from out of nowhere. Like I said I think another nuclear engine should be add because because we have a a ton of other gas engines.