re-usable test cases library

Hello folks, I have large amount of soapui projects (for an big application with > 25 rest-services), each per one rest-service.

All projects have an disabled test suite with "generic" test cases, that are re-used in other test cases (like user-registration, to be able to call other services). So actually it is hard to maintain that libraries in all the projects. Export from one project and import to all other wouldn't help: the IDs of some reused test cases are different in each project and there are differences .

What is your experience, how I could make an reusable test cases -library, that could be used in all soapui-projects?

thanks a lot!