analog to "with administrative privileges" for normal applescript

I’m working on a script that is needed to modify another user’s loginwindow.plist for administrative reasons. Unfortunately, i’m unable to figure out how to run applescripts as an administrator, or to do individual commands inside of an applescript as an administrator. I know i could use something silly like:

do shell script "osascript -e 'bunch of lines here'" with administrator privileges

but it seems to me that there must be an easier way than writing an applescript to call a shell script that runs an applescript!

here’s the example i need to accomplish with admin access:

tell application "System Events"
    set plist to (newhome & "Library/Preferences/loginwindow.plist")
    set props to value of property list item "AutoLaunchedApplicationDictionary" of property list file plist
    copy {|Path|:"/Library/Management/keychain.command", |Hide|:true} to end of props
    set value of property list item "AutoLaunchedApplicationDictionary" of property list file plist to props
end tell

Moved to AppleScript | OS X