As of Hibernate (version 4.3.11-Final) it seems, silly little me was trying to figure out how to annotate the entity beans with the cascade instruction. I didn't think it made sense to edit the PojoPropertyAccessor.ftl and the likes of those templates for this, much less manually edit the sources after they are generated. It was actually simpler than that, but maybe so straightforward nobody in recent years (up to 2013) bothered to describe how this works.
<foreign-key constraint-name="fk_1_2" foreign-table="tbl_2">
<column-ref local-column="id" foreign-column="id"/>
<one-to-one property="a" cascade="merge" fetch="select"/>
</foreign-key>
The Cascade will be annotated accordingly with your (all-lowercase) selection from either org.hibernate.annotations.CascadeType or javax.persistence.CascadeType; same difference.
