Lettow is a Ravnos. He settles in Tucson because this is where Aila fell into Torpor, but he's not entirely happy about it (more than in Maddyverse, I mean) and recycling between 7 different havens in Tucson is 1) very expensive and takes some time to set up, and 2) very boring.
Elisa catches his attention in this AU because of her spunk, much like in Maddyverse, but also because her being half Australian and half American means she doesn't really feel like she belongs anywhere, making her ideal Ravnos material.
... And then Pattermuster shows up and fucks it all up. The same night Lettow intends to get to her, Pattermuster gets there first. Lettow is furious. In this AU he still has Potence and other out-of-clan Disciplines and he and Pattermuster smack down, which ends in a draw. Pattermuster admires Lettow for holding his own so well and declares it water under the bridge. Lettow pretends to agree, but secretly he's still pretty miffed that Pattermuster "stole" his childe.
So when Pattermuster is like "uh, this is too much for me" and abandons Elisa, as per canon with the Brujah Courier, Lettow loses his shit at Pattermuster and actually manages to beat him in a fight this time. He doesn't destroy him, just delivers a message. Then desperately looks for Elisa to take her in because fuck you, Pattermuster, she was supposed to be my childe, well, now she'll be my childe!
In this AU, much like in Maddyverse, she ends up kidnapped by the Lampago, where she learns Animalism. Unlike Maddyverse, she doesn't stay trapped in the abandoned factory because of her bane -- the Lampago tries to keep her down there long as possible, but eventually Elisa gets so badly burned the Lampago ends up letting her go. Like Maddyverse, the Lampago keeps Elisa blood bound to her, but sends her on errands. Elisa is pretty much left to fend for herself in terms of havens when she can't stay at the factory.
((LMAO I FORGOT SHE'S NOT RAVNOS IN THIS AU I WILL EDIT WHEN I HAVE FIVE MINUTES TO MYSELF ADGFASDG))
Since she's not stuck inside all the time, Lettow manages to track her down much faster than in Maddyverse, and offers to take her in. Because of her blood bond to the Lampago, Elisa refuses. Not realising there's a blood bond, Lettow just lets her go. In Maddyverse, he sort of watched over her from afar and sometimes pulled strings to help keep her afloat when work for couriers got sparser and sparser, but in this one he leaves her alone entirely, and when the Lampago goes missing Elisa struggles even more than in Maddyverse.
It's not until the events of VTMNR when they meet again and Elisa mentions it that he finds out there was a blood bond. He's absolutely horrified and upset at himself for not pressing further at her initial refusal. Much like in Maddyverse, he feels a lot of guilt for her fate, if for different reasons. He also blames himself for Elisa's diablerie of Aila, much like Maddyverse. In this 'verse, she wasn't his childe by blood, but he'd invested enough effort into determining if she was suitable for the Embrace that he was still attached to her (though not as much as in Maddyverse), so he felt the guilt and responsibility all the same.
Also much like in Maddyverse, they fuck in this one too, bc I don't think there's a single AU where those two can meet and not screw like rabbits. In Maddyverse Lettow is the one that does the physical fighting because he's stronger, but in the CS!AU, Elisa does a lot of the fighting and Lettow, though he's pretty good in a fight too, relies more on wits and deception.