Groovy Grape dependencies can be a nice alternative for adding Maven repository dependencies at runtime (as an example please see my blog article http://rupertanderson.com/blog/r2-soapui-groovy-grape-dependencies/). To enable Grape dependency management it is necessary to add the ivy jar to SoapUI's classpath (needs to go in the /lib folder, rather than the usual /bin/ext/), making it a bit less of a standard bolt-on.
It could be a nice improvement to add Ivy to the standard SoapUI distribution to enable Groovy Grape dependency management in Groovy TestSteps etc out-of-the-box.
I have tested including Ivy 2.4.0 as part of the current 5.2.2 source in GitHub and it appeared to work OK - not that I have everything of course.
If other people think this would be a nice feature, please vote for this request and I'll pick it up and submit the change for approval.