Darrius is imo another one of those unfairly underrated characters. I think he's got some potential.

His MKD story completely confined him to Seido, so I'm interested in the kind of role he might play if he was more involved with the rest of the MK universe, how he'd interact with both the heroes and the villains. He was a grey character, morally speaking, and I'd like for him to remain so if he came back. I know it's a bit much to hope for the writers to make him something more than a straight-up secondary villain, but if they could just put a little effort into his story, it could be interesting.

He needs a more individual moveset, as all he's got that's really his is that turquoise projectile and a rather distinctive way of throwing it. That turquoise energy should factor in many of his moves, like it did in MKD. I think his gauntlet blades could become his trademark weapons, like Jade's staff and Kabal's hookswords.

I liked his design, and a new one shouldn't deviate too much from it. Keep the glasses, at the very least. I know some thought he looked like a black Gordon Freeman, but that's what set him apart, design-wise.

Finally, his "body reconstruction" fatality. On one hand, it'd suit Havik nicely (and he should definitely have it if he returns and Darrius doesn't), but on the other hand, it's nice that Darrius has something this unique that belonged to him. But regardless of who has it, I'd like to see how it'd be done in MKX, and there could even be an X-ray'd version of it.