MavenImporter is what you are looking, at least what you'd be looking for if it would be able to package EARs.
At this moment, you have two options:
1/ You can do some Archive delete/replace/merge magic - e.g. grab EAR from Maven repo and update only classes that were changed there
2/ You can use Arquillian Spacelift to the that manual step for you - e.g. deploy/install before you try to fetch
You can see example of both in Aerogear UnifiedPush Server integration test here, I've picked up Spacelift usage:
Hope that helps,