Not sure if he’d appear in the crossover, but there’s nothing stopping him from popping up at some point in Brothers Lost. Tiny Dean and Bowman would make quite a pair, and I can’t imagine the snark would ever end. Dean can’t pocket Bowman to solve his problems anymore. Now, he’s pocketable as well, so they better behave themselves or Sam will be encouraging Jacob to pocket them while he stays the lookout.
Dean meeting a small version of himself will always have his hands full XD But I can’t help but think how cute they’d be working on the Impala together. Big Dean has a little version of himself that knows all the car stuff he knows and is able to fit into all the tiny corners of the car, and little Dean has a big version of himself to boss around if he needs to move something heavy and they’d probably be on the same wavelength the entire time because c’mon. It’s their baby. She must be treated right.