I propose a scheme where official stable releases are uploaded to Debian unstable (if needed, selected patches from CVS can be applied), and packages based on tarballs like http://pike.ida.liu.se/generated/pikefarm/packages/7.%7B6,7%7D/latest [1] (but unambiguous versions would be preferred) are uploaded to experimental regularly.
Sure. Should it be automated?
It can be, but it can be a good idea with some manual inspection even when uploading to the experimental distribution.
We can move to packaging files to a separate module if that helps.
Yes, I think it would.
It's no directory listing, because the files named in it don't exist, save for the most recent one. Why is there no public repository of older snapshot tarballs (in particular, the most recent well-defined version would be of >interest)?
There is no repository of old tar-balls because they aren't saved. They are volatile pieces of source that should only be used for testing. If you must retrieve an old snapshot you can use the date tag shown in Pikefarm.
It helps if there is an official upstream tarball that you can compare the .orig.tar.gz from Debian to, but it's perhaps not that important in experimental.