Sucess! Syncing directly with Windows Media Player (12, in my case, from Windows 7) works perfectly. Artist info is as
I want it, not whatever the WP8 sync client wants, media info is much better managed, and with a simple (WMDMPreferredAudioBitrateValue1) registry tweak, all my desktop's music is automatically transcoded to 320kbps (if lossless; lower bitrates copy over directly, unaffected). Everything is exactly as I want. I'm content (though WMP12 is still worse than the old WMP11 on Windows Vista

).
*When I say artist/album info is as I want it, I mean the following: after I set it up properly in WMP, it is as I want it, even when I copy over to the phone. For example, albums with one main artist (say, Gwen Stefani), and a collaberation song with another artist, (say, Andre 3000), would normally show up with the normal WP8 sync client (even if I set it up properly in iTunes and WMP), as, "Gwen Stefani & Andre 3000," as a seperate artist, and with a seperate album. Syncing directly with WMP makes it all show up properly, in one album, all under one
primary artist.
As for cover art, I used some ID3 tag explorer plugin I've had for a while, I don't remember what it's called, however

I *think* regular WMP folder art should work, but again, I don't remember the correct way to get cover art in WMP, anymore.