Why, Dread? You're saying that DMC2 bosses are weaker ? I just didn't play dmc1 so I can't tell what bosses are stronger....
Another suggestion - Challenges, or something like "Jobs" mode. After you beat the game, these challenges offer you a whole set of missions, their plot taking place AFTER the main story. Like, Dante's ordinary, less epic tasks, "another day at the office". Here's the example of such episodes:
1. Dante gets an assignment to deliver a package to a certain person. Inside the package there's something that demons want, but the package is sealed. You need to know the basis only (the customer had the password anyway and the money is good). So you start in the city near the target and have to fight for it. Then, after you get it, run like hell, cause there's a demonic horde after you, facing which equals suicide.
2. Another work requires Dante to investigate a mysterious club, where hookers disappear (yeah, a pimp got the password). You get there and enter a survival battle with a bunch of enemies.
I can make up forms and modes all day! So, If you're interested, I may continue... Or should just make another dmc5 thread - "My version..." Just say the word !