Create New XML File In SharePoint?

I'm developing an org chart for my company and I want to spend some effort to make it interactive. I'm utilizing the Google Visualization API Org Chart tool and writing JavaScript to extend the basic functionality provided by that framework. This is the general plan that I've devised so far (note that I'm somewhat experienced with programming in general, but very new to web development):

(1) I need to store everything on my company's SharePoint site. So far, I've successfully uploaded an HTML file with some JavaScript that loads the appropriate Google Vis API onto the SharePoint. In the same directory, I've uploaded an XML file that contains some sample organizational data. I've employed XMLHttpRequest to read that XML file and draw the org chart. That seems to work well.

(2) I've written some JS functions to create new individuals in the org chart (at the Google DataTable level, not the XML level) and delete selected individuals. After the user makes these changes, I want to provide the option to save the displayed state of the OrgChart in a new XML file that sits in that same directory. I'm not sure how to do this. I've been searching on the web for a while. I don't know how to use the XMLHttpRequest object to create a new XML file on the server.

(3) Once I figure out (2), I'd like to also rename the other XML files to store old copies of the XML database so that I can restore data if I need to. I think this boils down to: How can one manage and rename files on the server side using JS?

Perhaps I'm looking at this using too limited a set of tools. If this is the case, please let me know and point me to the correct place. Remember though: I need to do everything from SharePoint. I doubt that I can load code or run processes on the SharePoint server because I'm just a simple SharePoint user. I can simply load documents (HTML files, XML files, etc.) onto the site.