Ahsoka Theory
My prediction/theory/idea, is that Baylan isn't really interested in Thrawn or anything related to him. He wants to access the world between worlds or something very similar/a very similar power.
I think we are now going to see that the world between worlds is intimately connected with hyperspace, hence it's ability to nullify conventional time-dilation etc. and act as a conduit through space-time.
Basically, I think Baylan wants the power to go back and rewrite Order 66. He justifies his actions of killing etc. because he thinks it will all be irrelevant once he's set things right. It will all be reset.
Baylan is therefore a reflection of Anakin wanting to save Padme, doing anything he can to accomplish it because he cannot let go of what he loves.
Ahsoka will see Anakin but also herself in Baylan because her thoughts so often dwell on her perceived failure of Anakin. Baylan will even tempt her with the proposition of saving Anakin etc. The idea that they can go back and change everything, make things the way they want them to be.
Ahsoka will ultimately decide that this is not the way, what's happened has happened and she must finally fully let go. Then she will fully adopt her status as a Jedi again.
I don't really know how this would end, but I kind of hope that, assuming this theory is correct, Baylan does succeed in his mission but that his task was an impossible one all along. He essentially gets the Kingdom of the Crystal Skull treatment. I.e. he tries to take the power/knowledge upon himself and gets annihilated by the sheer Lovecraftian weight of that power/knowledge. His mind crushed by the cognitive dissonance and his body destroyed.
