We have a document loader that works exactly like this using a Tidal job.
Tidal is our enterprise job scheduler. We don't have an end user drop
folder, however. We only use this for a system-to-system interface where
one system sends a file to the in box (folder) on the Windchill server by
FTP, then our job runs the loader every 15 minutes to find anything in
there, and upload it.
In our case, we don't revise this document, but choose to keep an initial
revision ("-" in our case) and either create a new document, or if that
number exists, then check it out, and upload a new primary content file,
and check it in with a comment if the document number already exists. You
could do this any number of ways - revisions, error out, whatever.
The code is fairly complicated with map files, and helper classes, and log
files, and JSP pages to view the logs, but it is doable with a goo
Windchill programmer.
Al