I have verified that switching between v2 and v4 based on the above-mentioned approach still works. After copying the older version into a different folder (in my case C:\Program Files (x86)\Leap Motion v2) and installing the newer version, I can switch from v4 to v2 using the following batch script (with administrator privileges):
net stop LeapService
taskkill /IM LeapControlPanel.exe /F
cd "C:\Program Files (x86)\Leap Motion v2\Core Services"
start LeapSvc64 --run
LeapControlPanel
and then back from v2 to v4 using the following batch script (again with administrative privileges):
taskkill /IM LeapSvc64.exe
taskkill /IM LeapControlPanel.exe /F
net start LeapService
"C:\Program Files\Leap Motion\Core Services\LeapControlPanel"