The replication of the DB content is not the related to the user that you are using for the operation.
Only the MySQL user must have enough privileges and you want to share extensions.
See the tutorial step 16 that present the concept and also generic keyword to apply the procedure on any website (at least to teach you).
There are 3 methods to install extensions.
1) Old method consist in re-installing the extension in the slave site as you do it when you install an extension in the master. The requirement is that the extension must already been installed on the master website.
2) Replicate a website where the extension is already installed
3) Use the JMS tool that allow you install/share/uninsitall extension and also sometime give you the possibility to propagate the installation to a set of children slave site.
This require that the extension are defined in the JMS tools and we are updating this list regularly to add new extension.
See the current list in
www.jms2win.com/component/content/article/135
YES with JMS you can also define "JMS templates" to propose a service to create website from the front-end. There is basic sample in the tutorial step 13.
www.jms2win.com/tutorial