Well, I'm not sure that using an interceptor for @Transactional on a transactional observer method is a "no-brainer" but since interceptor bindings are transitive the following binding should work for you (ie. could be used instead of the stereotype):

@Inherited

@InterceptorBinding

@Transactional(Transactional.TxType.SUPPORTS)

@Retention(RetentionPolicy.RUNTIME)

@Target({ ElementType.TYPE, ElementType.METHOD })

public @interface TxSupports {

}