I don't know if this helps you at all, but your post here gave me an idea. I did this on my Paperwhite 2 itself.
You will need to show hidden files and unsupported files. You can get to the text editor by long pressing on the file, selecting Open with... on the menu that appears, select the Text Editor radio button, then click on open.
I was just fine with the filename being the title. So I edited
found in
Code:
/mnt/us/koreader/plugins/opds.koplugin
I then deleted lines 541-543
Code:
if item.author then
filename = item.author .. " - " .. filename
end
And then restarted KOReader
After that, when I download with OPDS the filename is just the book title.