Scripting: Affecting Layer transparency in Layer Stack

Hi all, I'm interested in finding ways to improve our pipeline.

I know with Javascript you can parse the structure of a painter file, and SEE what layers are enabled. But I'm not sure if there's currently a way to SET what layers are enabled/visible?

Also, I'm not sure how to read what layers are selected.  But I remember Wes was working on a script way back to export selected layermasks, so I assume that's still possible?

Any help would be appreciated!