One problem with this approach is that we need a way for the heroes to know about the map and how it looks.

Maybe the map Ahsoka recovers could be a fake? That would show the audience and Ahsoka the looks of the map and explain the self-destruct maneuver of the assassin droids because there is no actual map to destroy.

So, you could open with Baylan and Shin freeing Morgan and Ahsoka’s little Indiana Jones adventure. Then during the meeting with Hera Huyang explains that the map is a fake and with no lead to follow, Ahsoka and Hera decide to investigate Morgan’s former operation on Corellia. They run into the hyperdrive core and place a tracker. Intercut this mission with Sabine’s introduction and her vision/dream about Ezra and add some form of a call to action. She then contacts Ahsoka and joins her on the quest to Seatos.