Cinema Blend offered a list of notable directors for DC properties, some of which are pipe dreams (Phil Lord And Chris Miller are too hot for most anything DC would have to offer them) or terrible ideas (a lack of a y-chromosome is not a good enough reason to give the director of the horrendous Punisher War Zone another shot,) but most reasonable. I'm unfamiliar with their selection for the Sleuth from Outer Space...
Who would I pick? Right now, without a ton of forethought, Neill Blomkamp or the Ford Brothers. I'd like my Martian Manhunter movie to be about something besides alien invasions and super-powers.
William Eubank's Manhunter
Lost in the idiocy of David Goyer's recent She-Hulk comments was his dissing of Martian Manhunter, while adding that they should probably change his name to just Manhunter. That last suggestion actually works, however: the hero known as J'onn J'onzz is the only original Justice League member not listed in the original plans. But he's a great character deserving of a contemporary reboot, and he needs someone with a great visual imagination. Enter Eubank, fresh off the recent sci-fi indie The Signal. Eubank has a sleek, commercial style and an interest in sci-fi ideas that would be appropriate for this more cerebral character.