Chris,

> Is there an option to get SWISH to output ALL of its indexed files? I 
> realise that for some this would be a really big list, but it could be very 
> useful in certain circumstances, e.g. if you wanted to filter the results 
> by some other method using your own software.

There is not an option for just the files, although it is is to add. 
(Perhaps in the next version if people agrees).
With -D -v 4 you can get all the info of the index file:
- header info
- words
- files
- stopwords
- metanames

cu 
Jose