I'm a bit torn on the unmapped plug-in issue. They can be safely ignored in the context of HV. Suppressing them adds quite a bit of clutter to the POM. I dislike this concept but I'm fine with it for the sake of an improved experience when importing the project.

I also don't like adding IDE related clutter. AFAICT we have a pretty straight forward multi-project build. No idea what Eclipse complains about. Maven POM's are cluttered enough as they are, I don't want to even add IDE specific settings.

I guess another issue is related to the referral to Java 8 classes from optional code, while the project is set-up to use JDK 6 by default

I am not quite following what the problem is here?