Re: future Superman/JL films must have DARKSEID, cast him !!!!
I don't think they need to overdo it with the CGI. Darkseid in STAS was always the same height as Superman, maybe even an inch shorter. And he was still menacing as hell. As long as the actor is good, has the presence and can sell you the fact that you don't **** with that person, height shouldn't be an issue.
Just look at Manu Bennett in Arrow. He's shorter than Stephen Amell, and is still utterly imposing.