To uninstall the client use the following line (you don't have to run this in a batch file):

"<windir>\ms\sms\core\bin\00000409\smsman.exe /U /Q"

"/U" = Uninstall
"/Q" = Quiet mode

If you want to uninstall of the clients on a particular subnet, simply delete the relevant boundary. The next time each client logs in, or on their next CCIM cycle (potentially 23 hours after you make the change), the clients will see they aren't assigned to any sites and will uninstall themselves. The Windows Management service will remain as will the "<windir>\SMSCFG.INI" file which shouldn't cause any problems.