Passing options to Data Export report format via testrunner

I'm looking for a way to customize the results data that is exported when running tests via testrunner.sh with the -R"Data Export" parameter. Essentially I want to filter out certain Step results by their type, and aggregate based on the containing Case. The default TestSuiteResults data provides only step name, message, time taken, time started, and status.

I've read through the Data Export documentation, and there is functionality for some customization via SubReport DataSinks; however, it only applies on the TestCase level (as far as I am aware).

Example

Custom Data Exported:

testrunner.sh proj -Eenv -ssuite -R"Data Export" -FXML -ccase

No Custom Data Exported:

testrunner.sh proj -Eenv -ssuite -R"Data Export" -FXML

Is there a better way to get more detailed test results data? Would a SubReport plugin be able to provide what I need?