For abuse this sounds fun, but as a test i think it's a waste of time.
Maybe you would had a better time picking up orphaned koyukkuris and test the Reimu's "maternal capacity" through "adopted" kids, if the Reimu can handle kids that aren't their own "paste" then she may have potential, if not, well, you just got yourself a nice stress reliever!
This may save you a lot of money if you won't give her a partner and will buy those expensive "pregnancy material" syringe thingies only to test if she's a worthy mother or not, and orphaned stray ko's are easy to find.
Of course for a better result i may suggest a diverse, both in attitude and species, koyukkuri group, to see if she can also tell apart the good kids of the bad kids, and if she has a species bias.