Hi @aembee ,
- Unfortunately per documentation [0], multiple Object Class Definition's configurations are not allowed - there are two params Class<?> ocd() (Required) & boolean factory() (Optional)

- Another way, If you try extending @interface annotation, per Java documentation [1] - No extends clause is permitted. (Annotation types implicitly extend annotation.Annotation.)
So, you cannot extend an Annotation.
Based on above assertions, to answer your question, unfortunately there in no way of referring multiple OCD's configuration. However, you can achieve that by defining those MetaType (@AttributeDefinition) in your original existing @interface which you are using in your component class.
OR
It might be much better to move the common configuration into some kind of configuration service, and centralize all common functionality there and use in other services using @Reference annotation.
[0]: http://docs.osgi.org/javadoc/r6/cmpn/org/osgi/service/metatype/annotations/Designate.html
[1]: https://docs.oracle.com/javase/specs/jls/se7/html/jls-9.html#jls-9.6
Hope that helps!
Regards,
Santosh