+1 This was certainly the idea when I added the name to an extension in 1.5.0. We haven't yet done anything with the name, but what I envisioned was something like:
$ asciidoctor -a extensions=ui,social,diagram sample.adoc
Of course, the API can take a more sophisticated approach, but once passed to the core we should end up with a simple list of names to enable.
I filed an issue to track this feature in core here:
-Dan