.bib file feels like a bit of a hacked together kludge. I mean, it works, but it ain't pretty, and it has some odd limitations. It feels like a replacement, built from the ground up to make the most of the power of biber and biblatex would be an obvious move.
Put the question a different, perhaps less provocative, way:
biblatex seems to be built in such a way that alternatives to
.bib files can be used. What alternatives are there that can be used in this way? The
.bib format was in place well before work on biblatex started, so
.bib files are not built for use with biber and biblatex. Presumably, if they were starting from scratch, they would do things differently with a custom-built bibliography database format for biblatex/biber. What would such a format look like? Has anyone tried to do this?