In the admin are we have now a Template Editor which allows your designer to edit the files used to set up a template for a client. These files include the template.css, template.js and the content of the template/images directory.
The code editors for the template.css and template.js files are simple as possible as there is much content in the css file and I prefer usability instead of fancy code highlights and submitting forms are handled by ajax this way allowing you to keep your cursor at the position where you left of the coding so you won't have to find the line you are modifying every time you update the files.
For the content of the template/images there is a simple file manager used which allows you to upload any kind of new files and even create new directories for you template.
You can access this new editor at:
Whit this feature you can now allow your designers to set up client websites without having to give them full ftp access to your sites.