Bunkers have an adjustment called Extreme which can be used to add one or two points to the bunker obstacle value for a hole. The definition of Extreme is:
If a pot bunker or other unusual bunker feature makes recovery extremely difficult (e.g., a tree within the bunker interferes with the swing or blocks the recovery shot, railroad ties or stack sod shore up the bank, or a large bunker on the line of play generates long bunker shots over sand to the green, etc.)
If my math is correct, adding 2 to the bunker rating for all 18 holes on the course would add approximately 0.2 strokes to the course rating and 4 to the slope.
Therefore, over the course of 4 rounds, it would add about 1 stroke for the scratch player. It would add about a stroke a round for the bogey golfer.