That's a good point that the concept would be notably different from the sort of Grimm we've seen thus far. But I'd be willing to wage that we're going to eventually see more humanoid Grimm in the future. This is obviously not only speculation, but speculation based on a hunch. It just seems like a reasonable assumption since it's a trend that so pervasively spans the entire genre. I would be surprised if it never came up. But, anything's possible.<br/><br/>With that being said: I know that the Grimm are supposed to be soulless, and if they don't say it out right in the show, it's certainly suggested that they can't match human intellect. However, I don't know if the ability to shift one's image would necessarily rely on intelligence. It could just be a hunting strategy that these creatures are able to change their physiology to look more attractive to humans to lower their guard the,<em>bam</em>: you've found yourself in the arms of a hideous man eating creature. Not exactly how a "real" succubus would operate ─ at least, not that I think, I'm stepping out of my expertise a little here ─ but it would still be interesting. We could always call it something else. In fact, I think it would be cooler to give it a different name. It would just so happen to be loosely influenced by the concept of a succubus.