Hi, maven-soapui-extension-plugin is not supported by SmartBear but by me and only in my free time (I don't have a lot these days)
Currently, the soapui testcase runner (in any plugin

) only supports a single project
For your tagging question, I have the following suggestion: you could use test cases properties and a groovy script.
in each test case, use the properties for tagging
in a master groovy script (runned before test suites of your project), find a way to retrieve the tags you want to use (java system properties, global properties, ...), loop over all test cases and desactivate those which don't match the tags
You would have to do this in all project
