I think telling it from a human, more than a metahuman, viewpoint is going to be one way to engage a wider viewer base. We want someone that the audience is going to have no troubles with - someone that they can easily slip into the "character" of.
With my "basic 4", I'd want to have 4 of the metahuman races; I'm thinking Human, Elf, Dwarf and Ork/Troll - I'm not really sure how I'd go for the last one - I'll see how the ideas solidify in my head as we go along.
As for roles, we need Guns, Magic, Matrix, Vehicles and Personality - so a Face, a Rigger, a Hacker, a Shaman/Mage and a Merc/Sam/Weapon Specialist. Yes - I know that's 5 - I can count - just saying these are the roles.