InfoPath Dev

I have read this article http://www.infopathdev.com/blogs/jo-anne_alfafara/archive/2010/10/06/side-by-side-versioning-with-content-types2.aspx. However, I have a need to use this process on an existing form library. I would like to use a slighty modified version of the current form as the old version refrenced in the article and add as a new content type a heavily modified version with schema changes. The requested changes include removal of several fields form the underlying xml. All while sharing like columns for same data. Is it possible to switch the current library to use content types and force existing forms based on original template to reflect visual changes of a slightly modifed version of the template while all new forms use the template with the modified schema.

Yes, just go to Advanced Settings and change to manage content types. Then, publish the old form template (with modified UI) and new form template as content types and link to the library. You will need to promote properties from the template to site columns and map those into the form library. You may also need to relink the old XMLs so that they open. Qdabra has a Modify PI tool that can do this in bulk. The default ShP UI doesn't support relinking XML to content types, but it's easy to manually modify these or use the Qdabra tool which is cheap.