Would like to recommend something where the paint strokes can be varied. Perhaps a programmable keyboard set of shortcuts where when the paintbrush is employed you could:
Press 1 = you get a drybrush beginning to your stroke, not only at the end (as if starting light pressure, pushing harder, then stopping the stroke OR getting light again.)
Press 2 = you get a stroke like the chisel brush is being twisted - thick & thin. Would be relly cool if this could happen if doing a drybrush stroke.
Press 3 = a brush like for ink like in Japanese caligraphy, where you can control the amount of wild side bristles and where the paint gets streaky in parts and runs out on parts of the brush stroke into something like streaks. (Not too dissimilar from what it can do now, save for the degree of streakyness)
Press 4 = a scumbling bristle stroke where you're grinding the paint for non-computer like scrapes, thin and thick spots, where it gets rattier looking rather than just smoothing out furrows.
Press 5 or 6 = a spatter technique that can be adjusted for the kind of spatter - very angled direction (somewhat oblong skipping) like from rapping the loaded brush smartly against the side of the drawing board for a mad grunge look (see Ralph Steadman), or conversely misting light dots somewht evenly like for stars.
Press 7 = rag smearing/reductive.
Press 8 = rag smearing/additive patting paint on with something that looks like a rag made mark (that could be adjusted to be smoother).
Press 9 = Badger brush for blending (looks like an old shaving brush).
Press 0 = a fan-like blending brush that is often used for fur or grass on oils.
And you could swap back and forth on the fly as you would for a real brush painting.
Just basically ways to make controlled and/or less controlled looking, emotional, expressive, non-repetative marks.