David-

Great post. As you know, I love Composer. I agree that it's a difficult thing to integrate into public-facing plugins and themes. It's wrong to expect all users to be setup, and willing to install and update Composer before using the plugin. This is one of the tricky things about GitHub, or similar, as a distribution system for plugins. Same issue with using Grunt. I think the solution is to maintain a latest stable, and latest dev, pre-built downloads as zip files.

That said, as a I developer, I love it, especially for deployments and building new sites in VVV, it can't be beat.

Take care,
Josh