Hello, Markus et al.
It's *much* harder for anything to become part of OpenJDK/Java SE than it is to be relevant and evolved elsewhere. I'd not recommend going on that direction. EE4J, like Java EE, is a set of APIs that make your life easier not only on Enterprise environments - CDI has now its Java SE target environments. So yes, it could find its place in EE4J, specially if other APIs use it (like Java EE APIs use each other to implement functionality).
If standardization is your need, and you need it now, you can use the JCP for that - while not perfect, it's been the (only) standards body for JCP. File a JSR, get your expert group formed and agree on a standard. It can be migrated elsewhere afterwards, as Oracle has done with Java EE. Also, the standard can be developed in the JCP with code living anywhere - GitHub, Eclipse, Apache....
If standardization is your need, and you can wait, wait for the standardization process of EE4J to be defined and follow the same path.
Going back to your original questions:
- Is there scope for common effort? I believe so
- Could it be done under EE4J? not now
- Or maybe just another toplevel Eclipse project? that's a very good way to start.
Regards,
Leo.