Going back in time would be a wise move for either the TV show or the movies, though in truth this one seems more like it would end up on the small-screen.
The Mandalorian Wars took place in the time of the Old Republic, and saw a long, brutal conflict between the Mandalorians and the Galactic Republic. It's the kind of long-form story that would play out well across a TV show, with enough to keep it running beyond one season (although there'd be the option of a Mandalore-themed anthology as well).
It's reasonable to assume Disney would give a Star Wars TV show a decent budget, meaning they could pull off the various big battle sequences, while it'd feature memorable characters like Mandalore the Ultimate, who leads his clan; Cassus Fett, which would provide a neat link to the main series while introducing a badass they could flesh out more than Jango or Boba; and of course Revan himself. We'd explore more of a cool, intriguing culture, still have recognisable elements, and enough plot, character, and action beats to fill multiple seasons of TV.