Minor Description
To support this dynamic requirement, the framework (as currently architected) would need to build an ObjectSpecification based on the Map instances being rendered, whose structure is inferred from the members of that Map.
I could imagine it would be possible to do, but would require some work within the SpecificationLoader. For example, perhaps the special-case handling here [2] could be extended to return a MapSpecification that handles the dynamic stuff... the issue though is that it would need to be told about a particular Map to look into. It would be hacky, but maybe putting the Map in question onto a ThreadLocal would suffice.