If you are really serious about running another copy or another version of SU, without it interfering with the registry then you should consider virtualization a version of your SU software.https://my.vmware.com/web/vmware/downloads
Example: I'm currently using SU 2015 as my main workhorse for daily work. Having found out that SU 2016 wont run many of my Ruby scripts. I created a virtual copy of SU 2016, also known as a Portable version, using vmware.
Warning: this process should not be attempted without a good understanding of Windows and what virtualization is.
Here is a short description of how I make a portable copy.
1. I always have a fresh bootable install of Windoz only, on a new UBS3 HDD
2. I install vmware and SketchUp on 1
3, With vmware running I make a new Bootable copy of SketchUp
Now I can run a portable version of SketchUp from my USB3 HDD or move that Portable to any other HDD
If you are competent in using vmware you can make versions that allow you to add addons scripts to your portable version, this is very important.