I just tried this version of Jemplode and the new file naming features work perfectly, exactly as advertised.

My filespec is now:
{artist} - {source} ({year}, {genre}) - {pos:2} - {title}.mp3

Which results in filenames that look like the following:
Béla Fleck and the Flecktones - Outbound (2000, Jazz) - 00 - Intro.mp3
Béla Fleck and the Flecktones - Outbound (2000, Jazz) - 01 - Hoe Down.mp3
Béla Fleck and the Flecktones - Outbound (2000, Jazz) - 02 - A Moment So Close.mp3

If need be, these can be translated into complete, fully populated tags with a simple run through Tag Studio. Perfect.

The only problem is that I forgot "position" started at zero. So the filenames are all off-by-one, but I don't really care since the only thing that's important is the order of the files, not the exact numbers.

I also noticed something interesting just now.

If you tell Jemplode to download an entire playlist, say "Yes to all", but then close the box showing the download progress, it keeps downloading in the background (closing the box doesn't cancel the download). Feature or bug? To me, it's a feature.