Do you need something like “Height” (or “HardMix”) mode ?:
I finally made a couple brush with “Superflat” tip that mimics “Height” mode (The essence like was mention before is to use mask brush tip). Still creation and, especially, editing those brushes is truly a headache.
“Fat” brushes is much simpler. There is already examples in “DA” pack and in the default pack e.g. “h)_Chalk_Soft” (similar like @Deevad shows)
And, yes, Krita definitely need some more textures modes.