You could create 2 report definitions each with a different template and associate both report definitions to the report, run the report with one report definition and then use the BI Publisher republish function using the other report definition. There is an option in the advanced form exit of the UBE submission that allows you to check a box to Prompt for Report Definition and the user could use the next desired report definition. If you wanted all of this in a single step for the user, you would probably need to do some coding or create an Orchestration.