Run UAT with a custom VS buildtools that were only copied but not installed

Is there a way how to point the UAT (RunUAT.bat) to run unreal with a custom VS buildtools (.net & C++ mostly) that are only copied but not installed on the machine?

We need that due to the continuous integration that we build that is going to test the plugins on different versions but pre-installing everything on the image is not an option we can take. We may mount a disk with all the buildtools preinstalled though and ideally would point unreal to use them.

The challenge is that vswhere will not know about those VS and therefore will not find them nor will unreal.