Yes it's possible. You might even be able to use the same report layout you've already created. (It depends on the details of your table and layout design.) Since sub-summary parts are only visible if the found set is sorted on the sub-summary's "break" field, you can sometimes control which Sub-Summary parts appear simply by sorting your found set on different fields. If this is not possible, you can set a script that uses the value in your drop down to select the appropriate layout and then sorts the records as needed to group the records as needed for the sub-summaries.
Define a global field.
Place it in the Header of your report.
Format it with your value list.
Use Format | Sliding/Printing... to set it to not be printed so it won't show in your report.
Create your script to sort and select a layout as needed.
If this is FMP 10, you can then attach this script as an On object/exit script trigger (drop down) or On Object/Modify (pop up). If this is an earlier version, you can place a button next to the menu field to perform the script. (Don't forget to set it to "do not print" just like the field.)
Great! Let me thrash through your suggestions and see how far I get. Many thanks.