This extension already exists and is our free Search/Replace plugin
www.jms2win.com/free-download/doc_downlo...rch--replace-utility
It does not work exactly like you explained but you can create Search/Replace list in a file on the disk and it is also possible to have specific list for each slave sites.
So you could configure the plugin a website that you replicate and always use parameters that are defined in a file on the disk.
So the user interface for the Search/Replace is not a Joomla component but a file (or several files) on the disk that you can manage with your FTP tool.
As this is a system plugin it works on all the elements of the page (modules, component, meta, ...)