Drupal admin themeing and customizations
Use https://drupal.org/project/admin_views
Go edit a view and add a new display: block.
Register a new path in system:

a) using hook_menu in your custom module OR

b) using https://drupal.org/project/empty_page
Place that new created block in a region (edit also the paths where block should be displayed)
I'm not sure what you mean by WYSIWYG editor in content area - do you want to edit node or what? 

a) If you used hook_menu, point its page callback into a function which returns WYSIWYG editor OR

b) If you used a empty_page you must create another block with editoror inside, and place it into content region