AppleScript should let you do this by using with administrator privileges:

osascript -e 'do shell script "sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist" with administrator privileges'

This doesn't pass the password, but prompts for it with a standard OS X prompt:

AppleScript should let you do this by using with administrator privileges:

osascript -e 'do shell script "sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist" with administrator privileges'

This doesn't pass the password, but prompts for it with a standard OS X prompt:

You can use this in your Automator workflow in one of the two following ways:

AppleScript should let you do this by using with administrator privileges:

osascript -e 'do shell script "sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist" with administrator privileges'

^{This doesn't pass the password, but prompts for it.}

AppleScript should let you do this by using with administrator privileges:

osascript -e 'do shell script "sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist" with administrator privileges'

This doesn't pass the password, but prompts for it with a standard OS X prompt: