It would be vital to geo-processing service debugging and testing if the the data formats of "Feature Set" and "Record Set" be properly supported on the Desktop.
If the parameter of the model has the data type set as one of the above (Feature Set/Record Set) then one should be able to load JSON from a text file on disc or point to a feature service in AGO/ArcGIS Enterprise Server via a URL (or exiting connection).
That way, one could get desktop pre-testing closer to the actual environment that will be encountered on the web where JSON feature sets and record sets rule.
This is especially important for python script tools where commands such as describe result in objects with very different methods/properties depending on the data format.
Does this not make sense?