Will you be adding other human factions/Groups of Interest like Serpent's Hand, a Janitor class or the GOC?

No. The amount of factions we have now is a fair amount, where each civilian is rescued by a certain armed faction and each armed faction has a certain civilian (also with Serpent's Hand, we really don't think the killing machines need armed reinforcements). We do plan to flesh out our already existing factions (D-Class, Scientist, MTF, CI and SCPs) however.