

If your concern is hard disk space, you could probably fudge something like what you want by using a hydrus tag archive snapshot of the PTR. If your concern is that you don't want to see all the remote files' tag results in the manage tags dialog, check out file->options->tags->by default, search non-local tags in write-autocomplete, which will set the autocomplete dropdowns in dialogs to 'local files' by default, instead of 'all known files'. The client never transmits which files you have to the server (to keep them private and minimise server CPU), so filtering can't happen before you download.

Once that's done, we've basically reinvented the hydrus db. In order to quickly query the ptr to figure out which of its mappings should apply to your files, we would have to store them in efficiently indexed database tables.
