I was asked to reply. I was aware of this thread, just had my reason to not reply yet 
Reason why I didn’t respond is because I wanted to do some research first and then do a more educated reply.
So take what I write for now with a grain of salt, I’m currently in a pinch between learning Krita codebase and art commissions, so I move slow
Problem is, I’m not sure yet if it can be done in current Smudge Engine without changing it fundamentally. That would break existing presets, which is a NO, NO.
It might need writing a completely new engine and one that would be actually two in one Pixel Engine and Smudge Engine it would be actually very close to Paint Storm Engine, at least its base features. (PStorm has some more interesting features than just that).
This is actually a very big project, and it was already on my ToDo list. Node Based Engine is even bigger. So I was thinking, that maybe I should first write complicated Paint Engine like that, to be sure I have deep understanding of PaintOps in Krita, or should I just make some improvement to old Paint Engines and then go YOLO with Node Engine
I also have to talk about it with Krita team and learn about their views.
I’m not sure yet what to do exactly and in what order, except that I should finish my current patches that I do to be able to understand Krita codebase well enough