With the observation that the road hole bunker hasn't been a static feature in overall depth, face steepness, size area of gathering influence, cuppy sand bottom, flattish sand bottom, sod wall face, grass steep face, depth of face, etc., I think as long as whatever would be there besides that bunker would need to have the same penality and potential to be as great as the traditional concept of the bunker. That seems to me to require a feature like a deep grass swale just as steep and requiring just as mighty of a blow and risk to get up from the bottom and onto the green without running over to the road. It still needs to have the size area of gathering which challenges both the bounding ball onto the green and the aerial assault, with the narrow safe runup area for a chance to run onto the green. I don't think a hummock convex feature can be a substitute. I think it has to be a deep swale or grass bunker.
Since I only played it once and my unfortunate result was to go from left to right rough and and didn't have a chance to optimally play the hole as it was intended, it is hard to say. I reckon only folks that have played it on multiple occasions and through its varied dimension changes and tweaks over the years can adequately address the question.