This would be really nice if it's possible. I have a map of HVAC equipment throughout our buildings, but each type of equipment is required to be in a separate layer for integration with a third-party application. In the web map I have each of these layers in a group layer and I was recently asked by our facilities manager to be able to see clustered counts of all equipment at each of our buildings when you zoom out the map to city wide. Right now, I can only set clustering at each individual layer which would not provide a total count of all equipment across all layers.
A workaround I'm considering is to publish a new layer for "All Equipment", append all the points to it, and just have it visible at the zoomed out scale with the clustering. This works fine, but it's another layer to maintain and make sure any new equipment also gets added to it. This extra bit of functionality would help out!
