I don't understand why there is no option to download only the part which is needed to render a single biab file (or a folder of biab files). I am pretty sure that the size of the necessary data is small and can be done in reasonable time even for the audiophile edition. That data could be cached so that no further download is necessary for a rebuild.

There are at least two other reasons for such a feature. First, you don't have to fill your expensive SSD with data that you never need and second, BIAB can be implemented on devices like an iPad Pro!