I think the only way you can make a node-based brush editor is by creating a new brush engine. Takiro is right that making a node-based brush editor that creates presets as they are currently defined for the existing brush engines isn’t going to work. The system doesn’t have the flexibility for that.
I think it was Sven Langkamp who started on a node-based brush engine years ago, but that never got very far. Adam Celarek actually made a scriptable brush engine.