I'm sure even in a series that focuses on non-force users such as criminals, the force is such a marketable thing that it's Likley a Jedi (or an ex one) will appear. Which is a strong point for dark times, Jedi left overs (before Rebels). Your very limited when it comes to force users in a post RoTJ show. With the Inquisitors existing, just another reason for dark times. Also not being limited to Rebels rating can present Inperial oppression/evil/danger better. Seeing an Inquisitor go all out against normal men could come to pass.