While there is no certain proof that Gaiseric is Skull Knight, it's very likely. On the contrary, nothing in the manga hints at Gaiseric possibly being Void (there is almost no information concerning Void at all anyway). That makes your supposition rather improbable.
On a side note, I recommend you to check older threads dealing with this kind of topic, they should prove to be interesting.
I'd comment as well but it would probably be a reitteration of what Aaz has already said, probably try to make it sound more poetic or perhaps add the chance that void is the wiseman Mozgus spoke of in his story, but in the end you'd probably be better off just sticking with his post.