I've been working on a new file system based on the origin private file system for a while. It's much more suited to large files that indexdb and is a step towards larger rom files on iOS. You can read about it here https://developer.mozilla.org/en-US/docs/Web/API/File_System_API/Origin_private_file_system

There's also a new syncing system which shows you the progress and the files that need to be synced. This is a step towards bulk adding of files