The challenge with trying to expand a displacement surface gets back to what the original intent was and how you’d create that displacement surface.
For example, if you wanted to do something fairly simple like a repeated dimple pattern, you could use a very simple displacement map to get a pretty consistent appearance. But it will become more tricky if you want something organic looking, or something which flows around a compound surface etc. At that point, you’d need to use something like Zbrush to build your displacement maps anyways.