Xtensions - Editable External Data parameters if populated in Data Lookup

It would be great if a Data Lookup using a Connection defined in an Xtension with parameters populated could be edited at the form stage when External Data is configured to use it. For example if a Data Lookup constructs a JSON request body containing several parameters if any of those parameters are populated then the entire JSON body is treated as a single parameter which prevents the configuration from being edited at the External Data stage. What I'm looking for is the ability to either present the blank parameters as editable at that point or give the option to edit any of the parameters coming from the Data Lookup (perhaps with a checkbox on each one to override the default value) at the External Data stage when designing a form. This would greatly simplify form design because we could reuse more generic Data Lookups while providing the value of having defaults.