Well, it's not a bad idea, I guess. But I'm not sure how much it will be used since most people writing a script would rather just dispose the windows manually than require the user to install a whole other script. However, it's nice if you have a series of scripts that you'll release as a compilation. One thing I'll mention is that you don't need to recopy the entire class, only the parts you want to change, so you can make the script quite a bit smaller than it is.
Also, you'll probably want to add an
unless $@
after the aliases in Window and Sprite, as you will get an F12 error otherwise.