Modernize the UI
The problem I have with Grafx2 is that it tries to be D-paint to the point of replicating unusable by modern standards UI. The tools are great, concepts (brushes, etc.) are simply amazing, but for anyone coming from tools like GraphicsGale or Aseprite, which are frankly functionally inferior, they simply bounce because of the interface, nothing else.
Yes, you can keep D-Paint philosophy and spirit, even its amazing shortcuts while having a modern interface. Just look at Pro Motion. And no, I'm not using PM because it's too damn expensive.
You should really think about modernizing the interface. All D-paint veterans are using shortcuts anyway while new users would benefit from more usable UI.