Well, anyone with actual root on a secure (locked, verified boot on) Android phone can hard brick it with a single command. Yes, you can yell at the user telling them it's their fault. Still something you usually do not want to support.

I don't think having authorized temporary root is inherently insecure, but on the other hand making sure it is secure could be a huge time sink.

Now, the original request here, modifying user app (I'd assume it's not system app) data, is reasonable. Designing a properly authenticated way to allow doing so would be an interesting challenge.