Overhangs with convex curvature are are a major source of print defects and failures due to the upward curling that invariably happens. Printing just these areas of the object a reduced speed would improve things considerably. Only the outer two perimeters really need to be slowed down. I'd suggest a speed reduction inversely proportional to both the radius of curvature and the overhang angle.
Overhangs with concave curvature would also improve with a slow-down, although the issues are different and the problems less severe.
Alternately, even something as simple as annotating the G-code to flag areas of moderate (say >35 deg) or steep (say >50 deg) overhang would make creating a post-processor with this feature much easier.