> and space and time for me to save it and extract it
One advantage is that for millions of small files, batching them together into one monolithic ZIP file allows for faster downloading. As opposed to a round trip to fetch each file. But there could be a happy medium where we batch 1,000 encrypted files to download to your computer then split them up, decrypt them, and cleanup any temporary files before fetching the next 1,000 encrypted files, etc.
> Is there any chance of implementing a hybrid of #2 and #4,
> a client-based, zero-knowledge option?
Yeah, we get asked for a "client restore option" quite a bit (see other comments in this thread also). Realistically I don't see it happening in the next 6 months, but eventually we really should get it done.