Discussing this with @jordwalke, we've reached the conclusion that separate compilation should really be its own independent option that you can toggle for any profile.

Actually, I'm thinking if it's best to have this option env scoped as well. It seems like we should be able to mix and match this stuff within a single project.

I still think that this option should be the default exactly as it stands today (as --dev is default) but perhaps Jordan some arguments against this.