Not talking about established retcons (like Dick's original Robin costume never also being Jason's).

Talking about potential retcons that they haven't yet done that you'd be onboard with, no matter how big a change.

Mine: Damian is actually the biological child of Bruce and Selina, conceived without Bruce finding out, and Selina not even knowing she was pregnant until she gave birth and, feeling overwhelmed, immediately gave up the child ... to an agent of Talia al Ghul, who feared she herself was barren. From there the sort resumes as usual. Until Damian finds out, of course.

Yours?