This has all the hallmarks of wheel re-invention ;)

Why not simply add the FileNewDialog to the toolbar in place of the New
command? This will give you a dialog box to access all the templates in the
User Templates folder, and on tabs that correspond to sub folder names of
the User Templates folder, which would be much the simplest way to arrange
your templates - http://www.gmayor.com/Template_Locations.htm

However to do it as you want, create a toolbar in a global template with
buttons to access a series of macros, one for each template each containing
a line similar to

Documents.Add Template:="D:\Word Templates\Template.dot"

(Change the path and filename to match the template)

then supply the global template as an add-in for your users.