Alphastream
Adventurer
Unless the alternative was that the DM could actually boost the adventure based on how many times his group has gone through it. It could be a somewhat challenging adventure for most people, but still get harder and harder for the well designed and played PCs. Add one monster to the entire adventure per unsuccessful time through and two monsters per successful time through. That, and have a lot of other DM options for adventure variability.
I see what you mean. I think the program is trying to be less "for the DM" and more "for the players" in that the DM is making a few changes within given options and the players are trying to best the set level of challenge. It isn't "DM, make your own challenge... are you the best encounter maker out there?"
Does that make sense? For example, the card players get is not something they can get every time. If they want bragging rights, they try again to get more boxes checked off. They also don't have to succeed each try to make some progress on checking boxes. The program seems to be really for the players to try to get these achievements (which is why DMs don't get a card).
I like your idea that the program could in theory have a scaling option beyond Nightmare mode for players. My question would be how often it would be employed. Most A-Team tables I know want to win and destroy. Oh, they want a challenge, but they want sweet victory. If the challenge is at level x and they best it, and they want to get more boxes checked, they want to again win rather than see it ratchet upwards in challenge. Not everyone will feel that way, of course, but I suspect most optimized teams aren't looking to play until they lose. The addition of nightmare x2, nightmare x3, and so on as check boxes may not be desired by a great number of players.
But, I'm curious. If you asked the optimized players that bested your challenge, would they want to play the same scenario again on nightmare x 4 mode? (Maybe add everyone takes 5 fire damage per round that ignores resistances, the place earthquakes every 3 rounds instead of on round 4, monsters have +2 AC and you get 3 times as many monsters...). You could always offer it informally, explaining the players don't get additional rewards. It could be an interesting experiment.