> unnecessary. (A high priority for me is to add HTTP 
> repository support, probably using GET/PUT to be compatible 
> with WebDAV. The only thing I need to figure out for a first 
> attempt is how to deal with getting a directory listing...)
> 

What do you need a directory listing for?  If you know the package name,
and each package has a continuous sequence of numbered .mcv files, you
could rely on the following URI convention:
/package-name.sequence-number.mcv

In that case, the client would do the following for each package:
-maintain a list of sequence numbers for .mcv files stored on the server
--ask the server for the URI: /package-name.last
-maintain a list of sequence numbers for .mcv files stored locally
-caculate the set difference
-build the URLs using the URI convention
-retrieve contents

It works well for the BFAV, in any case...  :)