There are a couple of experimental traps, check out the Wild Fish Conservancy website about it.

Eliminating gillnets will put folks out of work. GN is generally a one-person operation. Seines and traps require multiple people. What individual, whose success or failure sits squarely on him, wants to share his work with others?

Traps, for example, are fixed so you can only fish one place. In a given year a GN can work sockeye, pink, chum, coho, and Chinook by moving around.

I suspect the real question is what would it take to manage our salmon fisheries with minimal by catch, minimal waste, no lost-gear issues.

You might have more success on a ban and on changing public perception if the ghost net issue was brought to the forefront. Especially to publicize the killing of seals and birds. Since there are differences between I and NI gillnets one should be able to ID the broad source of the nets.