Here's a command you can use to assign permissions to a registry key. You can write this action using VBScript or WiseScript. As this script needs admin privileges to work, run this action in system context in deffered execution.
SetACL.exe -on "hklm\software\microsoft\policies" -ot reg -actn ace -ace "n:domain1\user1;p:full"
This command sets 'full' permissions on the registry key 'HKEY_LOCAL_MACHINE\Software\Microsoft\Policies' for user 'user1' in domain 'domain1'.