> You could imagine in the future, some associated highly flexible "owner" rules/notifications where a human can specify "I want to be notified if X system has a significant design change" and that intent can be recorded/managed in a more useful way than "add me as a reviewer if files in /abc directory change."

Good observation! If we share details about Antique, this will definitely be in there; this space is ripe for innovation.

For the "one blob per file" piece, blob storage is fairly cheap, but there is also a relatively simple way to get something like delta compression for blob storage that the clients never need to know about.