Have a look at http://www.avaje.org/bugdetail-94.html
Essentially you annotate your groovy beans with JPA annotations ... and then you can use Ebean as per normal (via "enhancement" or "subclassing").
I have not yet looked at anything further (Generic Dao or finder methods etc) so there is certainly more that can be done with groovy.
If you have further ideas, suggestions I'm very interested to hear about them.
Thanks, Rob.