every other exchange I know uses 1 eth for all assets
I think binance, kucoin and some other popular exchanges do not do this. They have different address for different coins/tokens.
Binance do that way, even those crypto which was started as erc20 and transfer to mainet with their own blockchain, still can get the funds if deposited to their previous erc20 address.
I wish you good luck OP, this is something so hard considering how unhelpful kraken to its previous case the same as yours.