Well, it would be cool to have it. It might mean slightly more change than I'd realised because I'd overlooked that at the start of the batch you actually get a dialog to confirm which folder you want. So I suppose I'm asking for an option which is "always use the default folder, without prompting, and re-evaluate it every time".
Amazing how there's always another complication when you look harder...
I'm only just starting, but currently I'm seeing more DVDs than I'd expected with generic labels like DVD_VIDEO, so it's definitely necessary to have something in place to protect against duplicate names. To avoid this, I've hacked up a Perl script that monitors my output folder and moves files out as soon as they are written, so I'm OK for now.
Cheers