I can confirm that this works, and will give you a true 1:1 sensitivity!
Here's how:
Open %LOCALAPPDATA%\TslGame\Saved\Config\WindowsNoEditor\input.ini and add this to it:
[/Script/Engine.InputSettings]
AxisMappings=(AxisName="Turn",Key=MouseX,Scale=1.000000)
AxisMappings=(AxisName="LookUp",Key=MouseY,Scale=-1.428571)
AxisMappings=(AxisName="WorldMapZoom",Key=MouseWheelAxis,Scale=1.000000)
AxisMappings=(AxisName="UI_MapMoveX",Key=MouseX,Scale=1.000000)
AxisMappings=(AxisName="UI_MapMoveY",Key=MouseY,Scale=-1.000000)
You will lose some bindings, I lost all bindings to A and S as well as a few MouseWheelDown ones. You can simply re-bind this in the option menu and they will stay. Making the GameUserSettings.ini file read-only did not work for me.