Choosing a Guardianship Successor via Will

Hello, my father is currently a guardian (legally through the courts) for my adult disabled brother. My father has a heart condition and has about 5 more years at best. Is it possible to have him sign over responsibilities to another eligible person (i.e. another family member) via a Will without having to go through the courts again? And if the above answer is no, is it possible to see a judge ahead of time to vet though a successor while my father is still alive? Thanks in advance, we live in Omaha, NE and this would be where the hearing would take place.