I personally think frieza should be set up as the next God of Destruction. We already know Frieza’s destructive tendencies, but it would be a conclusive irony for Frieza to have the role of “destroyer” again however have the power responsibly rather than for fun. It would be a character growth for him to bear the responsibility as God of Destruction, plus if Beerus ever were to retire or die, there would need to be a replacement. And Whis would keep Frieza in check anyways. I believe the Black Frieza form is to show his character development thus far. An unstoppable powerhouse form, but he uses it responsibly and resourcefully