The devs have put in some creative ideas. Mini monsters, missile launcher puzzles, mini bosses, etc. But there is a problem.
These aren't in older levels.
The devs need to put this in to the arcade levels. Dust bunnies in wolver dens, the puzzles in constuct levels, a randomly occurring boss fight in clockwork tunnels, stuff like that.
Of course, this would be in the Arcade Redux, so that means the devs need to continue that.