The idea of the "what if" scenarios makes me think of using queries instead and manipulating data in Excel via pivot tables (if its possible)...or by using a reporting tool. How often are these user-created db tables reused?
A lot. When the user creates the version, they will use the app just like they did when not using a version. This will include adding/editing/deleting/importing records into all tables involved. They may choose to keep the version around for a few weeks or
just a day.