I think you will have to do a lot of manual work to do this:
- open .xcodeproj with alt-click - Show package contents
- open the project.pbxproj file with a text editor Now find
/* Begin PBXNativeTarget section */, you will find a list of goals below. Here comes the part that is likely to force you to create a new project - there are so many cross-references by identifiers that need to be analyzed. You will need to find what you want to delete there. - xcuserdata,