You'll probably let other Software vendors plug extensions to your product. Since you are the author of the initial Software, is your responsability to organize it in such a way that the user can simply install the extension RPM and use it, without forcing him modify any configuration file. It is again the famous Install-and-Use that guarantees ease-of-use.
Well, and extension is nothing more that some files in a right format (DLLs that implements the API your Software defined), put in the right folders (directories your Software looks for extensions).
We can see many applications requesting the user to change configuration files to "declare" the presence of a new plugin. This is a bad approach that must be avoided because makes user's or plugin provider's life harder.
The most important thing to consider in your plugin architecture is to not share files between plugins and your Software. You should provide an architecture where plugins will be able to fully install and uninstall themselves by simply putting and removing files in specific directories, documented in you Software. Good candidates are /usr/lib/myproduct/plugins as the plugins directory, and /etc/myproduct/plugins as the plugins configuration files directory. Your Software and plugins must be sufficient intelligent to know how to find files, specially configurations, in these directories.
Using this approach, no post-install procedures is required from the user, and from the plugin provider.
I would like to close this subject inviting the reader a se abstratir and think about any Software can be treated as an extension to the lower level Software. In the same way a third party plugin is an extension to your Software, your Software is also an extension to the OS (lower level). This is where all the Integration (from the title of this document) magic lives. So we can apply all the ease-of-use concepts we discussed before to the plugin architecture design of your Software.