I didn't realize that we have any steel rim fans in the world....

Some sort of different brake pad is pretty much your only option. The chrome on the steel rims isn't all that thick and will not survive being sandblasted or milled in any manner. If you try it you'll just have rusty rims in short order.

What about the green pads intended for ceramic coated rims? Are those abrasive enough to cut through the water?

Also perhaps try getting pads that have a pointy end or cut your own so theres a boat like shape to better divert the water on the rim away. Same perhaps with cutting some extra water channels in the middle of the pad faces?

The old style "classic" brake pads used to have those multiple center round knobs. Maybe that shape was to provide more squeegee edges just for this issue?