I think you may just have to try it and see how it works. Those mechanical pluckers are wonderful things and might still clean the bird nicely. Or, more time consuming but maybe more appropriate is simply dry hand plucking. It's more labor intensive but certainly doable.
If you don't mind doing some education, I'm trying to understand your restrictions. I'm not that familiar with kosher butchering. The prohibition you're looking at is heating the bird (scalding or cooking) while the blood is still in the body? Don't you bleed the bird out before plucking, or so you slaughter some other way? I'm just going through my process of butchering. I slit the throat, let the bird bleed out, scald, pluck (by hand, wish I had a plucker!) remove intestines, rest, brine, cook.
If you're not bleeding the bird out at that point of slaughter, when do you get the rest of the blood out before you cook it? I'm honestly wondering. I knew kosher involved no blood, but now I'm trying to get my mind around the practical how's of this.
If you do try cold scalding in a mechanical plucker, please come back here and let us know how it goes. Once I do manage to obtain one, it would be cool to be able to skip that step if it goes well for you