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this is amusing because it reminds me of all the use case for P2 in gen 3 where it countertraps dugtrio, its cool to see trace still have a use case in gen 9. great write up!
I don't follow ADV super closely, but would using baton pass exclusively as a switching move aka no stat passing be balanced in the tier? It seems like a reasonable option to both preserve BP's existence in the tier as well as be healthier for the metagame.