Re: One more thing... And as you say, then Babs has to abandon her even though *she's* the one with whom it seemed to me (though I'm not an expert with Cass) she had the closer relationship.
In the arc where she runs off to fight Shiva, knowing she's going to die, she tries to leave a message to Babs - "thank you, for everything, you were like a mother to me." We never see her even consider leaving Bruce one. And Batgirl is Barbara's legacy, not Bruce's. Barbara discovered Cass, Barbara employed Cass, Barbara brought Cass to Bruce's attention, Barbara fed and clothed and housed Cass until Cass got stupid and put Barbara's secret ID at risk; she's the only person Cass has ever lived with other than Cain. Bruce adopting her isn't just stupid, hollow and obnoxious misreading of the Bruce/Cass relationship; it's a paternalistic undercutting of the Babs/Cass relationship, trying to claim as Batman's something that actually belongs to Oracle, an attempt to give Bruce a false primacy and re-elevate him to a central role at the expense of the other adult members of the Batclan (though at least poor Dick gets built back up elsewhere, as opposed to Babs, who's only been torn down more and more since).