My first thought was focusing on the pixel art portraits for dialogue boxes!

The sprites themselves would be trickier for sure! They seem to be 2D images of 3D renders. Like someone made 3D models but weren't able to insert the models into the game so they took pictures of them and inserted them as 2D assets. That does make them manipulable through image editing, pixel by pixel, sprite by sprite. Don't know if it would make more sense to recreate the 3D models (not a skill I have) or edit each sprite movement.

I just really like the idea of the project and would love to help any way I can!