It sounds like you have already discovered that attempting to install the older version on top of the newer will fail. I have the v6.14 apk available if you decide to root. Another possibility is to try deleting the exisiting Maps (7.x version) by pushing an ADB script to your phone from a pc (like the numerous debloat scripts on XDA Developers
). If successful, root would not be necessary. However, without root, you would not be able to install the older version as a system app… meaning that Android could kill it from running in the background in a low memory situation (not good for example, if you were using Maps navigation while something else was running in the foreground).