I would hold off on saying Milestone characters, they still need to get their feet off the ground in the comics. With the recent Milestone Returns Zero there was a lot of mixed reception to Static’s new origin and depiction of the other characters and if they chose to implement those versions into the films I think it would be a bit more controversial. Cyborg and Vixen probably don’t have the allure for a film but maybe a streaming property, but the thing with them is they have no source material and have pretty much played supporting roles. Due to the failure of Justice League Cyborg was not elevated in popularity nor was Vixen with her animated properties and appearance on Legends Of Tomorrow. These characters will be risky and due to their low popularity they may be more hesitant or reticent to pursue them in any form.