Hi
Since I'm getting value out of reading this thread, my conscience says I should mention my current project, even though I've only used dw for a sum total of 3 days in my life.
I plan to let dw users edit some individual page elements with Dreamweaver, individual files for things like "blocks", "left sidebar", complete with dummy content. I'm going to mark up these files with locked tags. Then another process will do the conversion into a real theme using these tags (the designer won't see that). The designer will need to follow instructions to make sure things are done right (eg. css files are correctly linked etc).
It won't be a purist solution, but then again my goals are not lofty. Simply allow dw designers to mess with a theme a little, and in a controlled way.
In the meantime, I'll keep reading this thread :)
Simon