The more I think about it, the worse the deal looks to me from the perspective of the 11 young women.
They get sent to live with a different clan.
They're at the age where they will want to get married soon- but it will be hard to find a husband who would agree that any babies born in the first five years will be taken away.
They go through pregnancy and childbirth, and immediately the baby is taken away. Even if they agreed to this arrangement in theory, they might feel very different about it when it really happens.
Finally, at the end of the five years, they are free to have a normal family experience, but by that point their society will regard them as "over the hill."
If main thing the Uchiha get out of this is the Kurosawa bloodline, why adopt the girls into Gouketsu and adopt the babies back to Uchiha? Why not let them stay home and have a more normal life, and offer the Uchiha the means to do artificial insemination? (It would make sense that this didn't occur to anyone until now, but we can suggest it.)