David, while it might be a little dangerous, it might be worthwhile to offer a true, dumb mirror option, to account for the situation in which someone has used something like FileZilla just to do one upload, resulting in a non-synched manifest file. In short, it would say, "I'm going to upload everything in the current local album to server directory X, and anything that's sitting in directory X that isn't in the current album will be clobbered."
Usually, if the album is destined for a subdirectory of the domain, that would be safe. If it's targeted to the root of the domain, however, it would usually be a bad thing to do, since that's where the server is keeping all sorts of other account-related files (especially things like .htaccess). In fact, it could be very ugly, indeed.
Or maybe do the mirror for all files and folders
except the top level of the album. A server wouldn't be stashing files in
res,
thumbs, or
slides, for example, and probably not in any album subfolders at all.
Just thinking out loud, since I've been in this situation myself.