Replacing exisiting templates with new design

We have a new template design that needs to replace the existing one. Because of the amount of departmental specific pages in use we have 40 different page templates with widgets that have been added at the template level. Each of these templates have several styling assets or widgets that need to be updated for the new design. We are trying to push the new design live as soon as possible. Is there a faster way to update these page templates using shared widgets or assets with out having to manually update each one?