I don't recommend a challenge like this first, and here is why: One of the most satisfying things about completing a challenge, at least in my opinion, is having the self-proving and amazing save file.
For instance, when you load up a completed Excalibur II game, you have Excalibur II. It's proof you got to Hades within 12 hours and that's something to be damn proud of.
When you load up a completed level one Ozma game, there you are on disc 3 with the key item proving that Ozma has been defeated, and every member in your entire roster is level one.
It's awesome, and you can show your friends and always have that save file as a reminder of what you accomplished. Now comes solo-character or command-barring challenges. Load up a completed one, what do you see? Sure, your other characters might be down on levels from being dead most of the game, but really it looks pretty much the same as if you'd used all your characters and all your commands. There is nothing really special about the file, and after all the work you put in, it's sucks not to have that.
That's my view on it, anyway.