He actually was in the universe on Criminal Intent as Goren's bro & got smoked IIRC.
Branch and by extension til he took over, Jack, in that DA role is just one of them things where its hard to see anybody else in fr. Gonna have to give bro some grace for sure cuz it's gonna look weird at 1st. Shyt, between SVU & OG L&O, they both feel weird with how they're shot now camera wise, stories they choose to focus on, and all of the revolving door of characters. This is just another component.
This is why I like Organized Crime so much though. It's a fresh & new L&O so they got to carve their own style out from scratch and the consistency is still their for the most part cast wise since they only like 3-4 seasons in. No history to compare it with or "good ole days".