Well, writing in sed has essentially the "heh, look what I did in sed!" value. Elisp would be a far more simple place to build it (we already have tetris there, there's even a very old simple version of Elite in emacs lisp!)
Yep. "Real programmers write games in sed".
I'm sure Emacs has a "unix mode" hidden in there somewhere. Inside it, I bet there's a full complement of GNU utils. Sed should be in there somewhere.