My idea is a WYSIWYG Editor modul which helps to manipulate OneUI themes. The user can see a sample page of the OneUI theme, where he can click on an object, this opens the object properties and other elemnets. Then he can change them. Of course the sample is changing also. eg: he clicks on the header, then he can see the company logo, background, etc. He changes the bgcolor, and uploads a new logo.
When the editing is finished, he can save it as anew theme and upload to the server. The editor should be able to list and view all existing themes, copy and delete them, distribute themes across servers (in a distributes environment), etc.
I hope you like this!