I believe that Shin(The Multi -Eyed freak) wants Sarada only as a leverage over Saskue as she is his daughter:-
www.narutobase.net/manga/naruto-gaiden-the-seventh-hokage/3/11/
and He isn't looking to recruit Saskue but wants his Rinnegan:-...
are we all taking the theorizing a bit too enthusiastically? because i mean kishi is unpredictable and has known to mix up all lot of different religions to create the series. personally i love reading them but i believe thing are going a tad bit overboard. if go simple you may be able to...