Icon has been labelled as The Black Superman and this seeming redundancy causes him to get disregarded. (Even though Superboy, Superboy Prime, Supergirl, Captain Marvel, Black Adam, Mon-El/Valor/M’Onel and the whole planet of New Krypton don’t seem to have that problem).
Hardware has already made an appearance in The Brave and The Bold teaming up with Blue Beetle and even though he was the typical “angry black hero” who doesn’t want to team up with Jaime, at least he was being used. AND the issue hinted at what could possibly be a long term storyline for Hardware. Personally, I just want him to start a new company with John Henry Irons because I’m sick of Lexcorp stuff being everywhere.
Blood Syndicate isn’t technically one character, but they have almost always been treated as one monolithic entity and a lot of creators have rarely used just one or two of the individual members. Not to seem to glib about it, but I’m not even sure if most people are aware they have names.
Of course, the one Milestone character (outside of Static) who will probably get used in the DCU is the top Milestone villain (sorry Alva): Holocaust. Not only is he an angry black drug dealing gang banger with a secret middle class background but he has the added benefit of being offensive to a lot of the Jewish population.
Of course there are other characters, but these are the big ones.
Like I said, I just hope DC does a better job with the Milestone character than Marvel did with the Malibu characters.