Their pitch: make beautiful sites with a simple interface that doesn't require code - and export it to HTML/CSS when you're done.

What I'd like to do is IMPORT code - and tweak the design from the interface.

Any web services offering this type of interaction?

My specific intent is to throw up a BlackTie Boostrap Theme[2] and edit it to suit the project.

[1] http://webflow.com [2] http://www.blacktie.co/2014/05/studio-one-page-theme/