I have been looking for a solution to remotely remove the SEP client and I couldn't seem to find an easy solution but I think I created one earlier that has worked on a couple of systems so far.
I used SEPprep from the install media to uninstall any existing AV already on the system, including the Symantec endpoint client. You'll have to read the PDF that comes with SEPprep to edit the ini but I had to make very few changes for our environment. I also used ClientRemote.exe to push out SEPprep. I have been using ClientRemote to do all my installs since upgrading to 12.1.6 MP3 and it is located on the SEPM server at this location. C:\Program Files (x86)\Symantec\Symantec Endpoint Protection Manager\tomcat\bin
What I did was copy the SEPprep folder to where our deployment folders are located on the SEPM server. Go in to the SEPprep folder and rename the SEPprep.exe or SEPprep64.exe to setup.exe then edit the ini to run silently and not prompt to remove. After this I ran ClientRemote.exe and pointed to the renamed setup.exe (SEPprep64.exe) and pushed it out to our clients. It is very fast and once rebooted our new AV installed without any issue.
Interested to hear thoughts on this or if you run in to any problems.