They should let this series demonstrate its uniqueness and its intention to push the envelop further, by starting off with a film about HugoStrange and his Monster Men.
Next up is a film adapting the exceptional storyline Prey, with HugoStrange becoming the main villain again and sending a new masked vigilante out into Gotham to hunt down Batman.
HugoStrange will have already been in each film as a supporting character (and as the main villain in the first film), and in this film Strange is hired by Black Mask to try to develop a psychological profile on Bruce as a way to find his weaknesses.