Hi - when you say make 4 - 5 copies of the form ... maybe it would be easier to publish as a content type? Then use the content type in the different libraries? When you create a new XML with a template, you'll see in the XML (open it up with a text editor) an "href" attribute that links the XML to the original template file. So if you move the XML from one library to another (changing where it is submitted to), it will still have the URL to the template that should open it - that shouldn't cause you an issue necessarily, but I wanted you to be aware of it.
As far as updating your old forms to open with the new form - well, if the data structure in the new form is different, you'll probably need to create an XSLT that can be applied to your existing XML to transform them - that can get a little technical.
I don't really have any good ideas for hiding "new" in a form library except to use SharePoint designer.