In all honesty I think Kishi should make a Jiraiya series. Why Jiraiya?
Because Jiraiya was one of the only characters in the series to interact with just about every major plot character in his generation of older.
With Jiraiya series we would:
Know more about Prime Hiruzen
Know more about the Sannins
Know more about Minato
Know more about Danzo
Know more about Root development
Know more about Kushina and Uzumaki
Know more about the Second Shinobi World war
Akatsuki early upbringing
Uchiha pre rebellion
Land of the Mist during the fourth Mizukage
Konoha Elders
Minato's teammates
Among other things
Thoughts?
Because Jiraiya was one of the only characters in the series to interact with just about every major plot character in his generation of older.
With Jiraiya series we would:
Know more about Prime Hiruzen
Know more about the Sannins
Know more about Minato
Know more about Danzo
Know more about Root development
Know more about Kushina and Uzumaki
Know more about the Second Shinobi World war
Akatsuki early upbringing
Uchiha pre rebellion
Land of the Mist during the fourth Mizukage
Konoha Elders
Minato's teammates
Among other things
Thoughts?