Agreed. I don't think the range would need new 'human' figures, just some variations on existing monster miniatures. Such as Greek fishermen with the Innsmouth look, or a moldering corpse wearing a fine senatorial toga. The monsters wouldn't have to be specific to the Mythos really, just having a line of Ancient Horror miniatures would be enough.
Would be fun to play, but I doubt I'd invest in new minis for it. Personally I'd probably just make due with using the ancients I already have.