I don't know why people see it as so ridiculous to give a little girl MS. The eyes aren't based on age , just trauma. Itachi and Obito both awakened MS at around 13.Heck , the little Shin clones already have it. Sarada is just a little younger currently than the ages that Obito and Itachi were when they awakened it , and she looks to be (in my opinion) older than the Shin clones. Therefore I don't see why people thinks she is too young.
Also , I don't think she'll go blind from her MS. Sasuke has Hashirama's cells that were given to him by Kabuto. He also has Hagoromo's chakara. Therefore I think it is feasible that Sarada could be like Indra or Obito and have a mangekyou without blindness.