Well, that'd be cool, but the enemies should be able to take damage.
That reminds me of a mode that I'd thought about earlier. A mission creator. Every few missions you beat, you get an item called a "mission set". Normally, Mission Sets are useless. However, exchanging them at the divinity statues gives you new things for the mission creator, such as objectives, rooms, and bosses/enemies.
In addition, you can set the difficulty level, and place key items to open doors or solve puzzles. For example, let's say the mission editor was in DMC4. Then, if you wanted to make a mostly vertical level, you could have the player start with the Wing Talisman and put a bunch of Wing Steps around.
All I'm really trying to say is that it would be pretty freaking cool to make your own missions.