It would be really cool to have a vtuber lighting option like Vtuber Studio, where you can make the vtuber darker with the eyes or other parts shining to emulate a light-off situation (if possible, along with this idea, there could be a button on the custom objects that would turn on whether they would be affected by the lighting or not)

example video: "VTubeStudio - Scene Lighting Customization" from Cutie Dragon on Youtube

I believe that in vtuberkit it could be a more simplified version like just a "brightness selector" where you can define a value for the vtuber brightness along with this buttons on the eyes and custom objects to be affected by the brightness or not

Also a mouth tracking would be great, for smiling, neutral and sad (it could be something with the available mouths)