I've been playing with the idea and I came up with a little "patch" that may be added to a channel and will try to fix this issue. Here's the link to the repo:
https://bitbucket.org/czukowski/plex-locale-patch
I've tried that with my channel and now it suddenly appears translated not only in Plex Home Theater and Plex Web, but even when I look at its raw XML in a browser! All of it after adding only one or two lines to the channel code.
See Readme (or the source code) in the repository for more detailed description.
p.s.: I took the liberty of marking this post as a solution.
