Well, among others, Kodak used ethylene diamine as a silver halide solvent that was mild and did not cause excessive dichroic fog. They also have used thiocyanates as you mention for solvents, along with other organic solvents that repress dichroic fog just as the benzophenone does.
Lets consider this one solved. You all get a feather of some sort or another for really good answers. Thanks. Additions are still welcome though as there are more specific examples out there.