Potentially naive question - If I had a non-user-facing CRUD admin backend, why should I not use this for validating the data while creating or editing records?
If you already have validation, hand tuned and correct, it will perform better. You will have overhead during the encoding to validate in CUE. This may not be a concern, also CUE has some performance goals that should make it a non concern as well.
Why not give it a try with some experimentation?