sorry if this is weird but you're talking about the RR au and how you don't know how to role swapping you don't that's why it such a good writing teeing
You have a crossroads. The first crossroads is whether Bruce Wayne exists and only Robins are reversed. If the answer is yes, this world will focus on the interactions of the characters, their similarities, and their differences. If the answer is no, then this world will change completely into something dark.
We're talking about the loss of one of the three pillars of DC,how will this affect Gotham and the characters associated with him? What changes were brought about by Batman and Bruce Wayne that are now gone? Make the readers feel his absence, as if it were haunting the narrative for the readers, and the characters. Who would Duke Thomas be in Gotham without Bruce Wayne and Batman? Who would Damian be without his father? Who would Tim Drake be without Batman or Bruce Wayne? and don't make the don't the answer, oh, they're fine, nothing has changed because it's bad world building
2/ let say Bruce is batman < cuz I don't like the au without him> who he would take first? Duke or Damian? Let take Duke and now the fun begins
What are the similarities between Bruce taking Duke and taking Dick? What are the differences? Now Bruce's first child has superpowers. Will this strengthen his relationship with Clark to resemble the one when he took Dick? And what about Duke's past, his evil biological father, and how Batman in his early days, might Duke parents have died from the Joker's poison because there were no advanced treatments available? And you can take Robin because Robin being a nickname from Mary Grayson is relatively recent in comics, and the main reason for the name is that Dick literally loved Robin Hood. You could give the same reason to Duke
Now you can let Duke and Bruce's characters drive the plot, while also giving some, but not all, of the traits we know as Dick. For example, he grew up as Bruce's only son for a longer period, and he became the leader Bruce relied upon because he had worked with the Justice League almost from the beginning.
How will the fact that he has power and Bruce doesn't change their relationship?
3/ Damien. Now, was he brought to Bruce for training or a shelter from LoA? How would it change? He's home alone with Bruce now that Duke has moved out, and this Bruce is still younger. He's the same Bruce who raised Jason in the main world. Don't forget that. Of course, Damien will die, but Talia won't let that happen, and Bruce knows it. < don't rely on the canon here we have different characters who are only in similar situations >
I find it a nice way to study characters and their interactions, but most of who write them just change and give them different personalities without referring back to their original personalities before they met Bruce and how they differ. I don't want to annoy you more, I hope you get what I try to say
I get it. I still don't get it, but I get it.