So working with base Honey Select 1 and 2, I've noticed a few deficiencies that maybe more research might go into rectifying down the line, or mods/someone else who really knows what they are doing might be able to help with. I've noticed the following:
It seems like Honey Select treats certain features in kind of a cookie cutter manner. As such, the eyes, nose and mouth are kind of... "glued" to the surface of the face. There are certain parameters you can alter with the sliders. However, you'll notice that it seems like you can't make the ultra realistic facial expressions of some people from pictures taken in real life due to limitations such as the mouth being cookie cutter. You can scale it up, but you can't do something like implement an overbite or an underbite, and the existing expressions also don't allow for that. As such, if you want to implement say, a porn star's lip bite, you're going to have a bad day. People in pictures also tend to look a tad different depending on lighting, angle, and expression. For one thing, when you're smiling, your jaw kind of pulls certain muscles in a way where the entire shape of your skull as a whole gets altered. Some parts of your lower cheek get puffed in while your upper cheek gets puffed out. At the same time, your jaw might have a tighter line than if you were in a neutral expression. Because Honey Select sculpts the entire head's shape, and then pastes on the nose, mouth, eyes, it seems to me that getting the hyper realistic look may be a tall order. As an example, when you smile, your eye depth may look like it is changing, because your cheeks suddenly have a higher depth. But its distance from say the bridge of your nose/forehead partially depends on how the muscles in those regions of your face are drawn. (We subconsciously squint when we're smiling for real).
This is stuff I've noted when I was playing with Blender's KeenTools facebuilder and trying to sculpt some characters in Honey Select. Research is still ongoing and pending though, so maybe I'll eventually be able to work around some of these limitations.