For example to automate what couldn't be automated otherwise.

You've always had this ability, but with more convoluted syntax:

  osascript -e "tell application \"System Events\" to keystroke \"whatever\""

Specify the application too with multiple -e parameters. This will copy whatever is selected in Safari:

  osascript -e "tell application \"Safari\" to activate" -e "tell application \"System Events\" to keystroke \"c\" using {command down}"

Ahk isn't cli, and also is a full-blown programming language, so not as limited in its input