Why Namek? Why not set it sometime between the destruction of Vegeta (if you wanna avoid Saiyans, which I get) and the start of the saiyan saga? That's a good almost 20 years with no saiyans to speak off where Frieza's empire was at it's height.

Exploring subjects like his rivalry with Cold and Cooler, too. Fight Cooler's cronies for territory, etc.