Months ago I suggested Painter include a bruah possibility similar to Photoshop: (examples available on YouTube)
1. allow for "dual" dab brushes
2. add characteristic capability that Photoshop brushes have called "impressionist" (checkbox on/off) which is not like any Painter impressionist brush, but rather extracts colors from a sample image...a bit like auto painting using image (not color wheel) colors; but from the selected image range like color mixing via color mixer panel and sample multiple colors.
And now, with my experiences using Rebelle 6 pro, I've become enthralled with sometimes using brushes where the brush dab/shape/grain/texture (up to 4) can have multiple shapes+grains in user controlled order (sequential, random,pressure, tilt) using their Brush Creator panel gui.
These types of brushes offer incredible control and more natural/organic results with less user brush manipulations.