Hi there,
I'm also new in soap UI. So don't take my post too serious.

My understanding is that we need to add another sub-report type and (probably) implement new data source type (similar like PropertyReport does) then this sub-report can be included into another report.
However it would be good to have the report included into the soap UI pro installation package.
Or at least some implementation sample for it from eviware experts.
So far I found 'JasperReports Tutorial' in the google which I believe provides general idea how to do it. However I'm not sure if it is applicable to the soap UI.
This is code example to get assertions for 1 request step:
def testStep = testRunner.getTestCase().getTestStepByName("Test Request")
def list = new ArrayList()
def count = 0
for(assertion in testStep.getAssertionList())
{
count++
def item = 'Assertion #' + count + '. ' + assertion.getName()
list.add(item)
def assertionErrors = assertion.getErrors()
if (assertionErrors == null)
log.info('Successful')
else
for (error in assertionErrors)
{
def errorItem = 'Error: ' + error.getMessage()
list.add(errorItem)
}
}
for (l in list)
log.info(l)