Difficulty mod for PC
It's starting Asaic... 
I guess it's better than nothing. It's not really my thing though.
I don't really consider less life for you and more life for the enemies to be "difficult" per se. I don't equate endurance and tedium with difficulty. This concept is more of a lazy designer's version of 'difficulty', which you see in a lot of games. I was never a fan of it.
I would relate this concept to adding more "challenge" to something like NASCAR by simply adding another 500 laps and more cars. To me, adding actual difficulty would be making alterations to areas of the track and including opponent cars that explode if you bump into them, or things like that. Interesting things that challenge the way you think, rather than just encouraging you to endure more of the same old thing. IMO, challenge should foster interest, not tedium. 
Now if people can actually tap into the AI in AC2 and make changes on that level, then I'll be interested. 