Hi Matthew,
Getting a bit ahead with the Office 2015 reference - we have no idea how that will work. Quite apart from toolbar issues, migrating to Office 2007 & later can break some existing code. Application.Filesearch, for example, is no longer supported. Andreas Killer has made a replacement class module you can download from:
http://dl.dropbox.com/u/35239054/FileSearch.cls
For a discussion of how to use the class module, see:
http://answers.microsoft.com/en-us/office/forum/office_2007-customize/dir-vs-filesearch/9021a162-7ec5-4c16-bff8-84f28300dba4
As for the interface, All we've got to work with now, in terms of changes from Office 2003 & earlier, are Office 2007-2013. Office 2007 provided little support for user-customization of the Ribbon. Office 2010 is better. For the basics of Ribbon customization, see:
http://gregmaxey.com/word_tip_pages/...bbon_main.html