yes I agree about locating some option on @Indexed, just make sure it's clear that it's relating to the annotated class, not (directly) related to the index name.
For this kind of changes the best approach is to write a proposal of the new API to the developer's mailing list; see:
https://lists.jboss.org/mailman/listinfo/hibernate-devUsually I'd suggest to make a proof of concept, with unpolished code and some tests, to make sure what you propose is actually implementable, and get a better grasp on how it would work, what the limitations are. Then you propose the API, we discuss the details like attribute names, annotations, etc ,and when that is settled by a broader agreement we can work together to polish the patch, and merge it for inclusion in the next release.