First of all, thanks for your patch, and sorry for the late response - somehow, I must have missed the first notification mail.
Please always provide before/after screenshots in review requests which change anything in the GUI.
Before we discuss the code, the following questions should be addressed:
1. Considering that all the new codes which are shown in the dialog might confuse users who do not need them: is the feature useful enough for enough users to justify this?
I see that including this advanced renaming feature in Dolphin directly instead of using a tool like KRename might be more convenient for users who use such a thing frequently. However, a good alternative might be to put this feature into a context menu plugin, which could be installed by anyone who needs it, and which would not harm the usability for users who don't.
2. I'm not sure if the design of the dialog is optimal. Users who are used to the simple "add an ascending number" rename mechanism might be overwhelmed by all the text explaining the options.
I suggest that you add the usability team to this review request (after adding before/after screenshots). They have provided great advice for dialog design in the past, see, e.g., http://sessellift.wordpress.com/2014/05/01/the-little-things/ and they might also help to judge the question "do we need this feature in the default file manager or not".
I see two ways how your approach could be modified, but there might be more:
(a) Put the advanced renaming feature into a context menu plugin (such that there would be an entry like "Rename (advanced)..." in the context menu, which would then open this dialog, for users who install and enable the plugin).
(b) Keep the existing dialog as it is, and only show the advanced options if the user clicks an "Advanced options..." button.