We are refactoring our project and are trying to clean up the usages of templates throughout the project. There are a number of templates that are very similar that could all be using the same data template, which would also mean we can better utilize the "Compatible Renderings" functionality in Sitecore making it easier for editors to change components.
The problem is we have existing content and it would be a pain have to re-create all the datasources and copy across the data manually.
For example, given the following data templates:
Title1 Single-Line Text SubText1 Multi-Line Text Body1 Rich Text Image1 Image
Title2 Single-Line Text SubText2 Rich Text Body2 Rich Text
How can we change all items which use Template B to instead use Template A and still retain all existing data?