The problem with the difficulty level is you're taking a level that must by necessity have a number of low difficulty challenges plus a wide scope for those challenges and are transforming it into something far more limited.
Do you then try and keep the same overall difficulty (Say number of times needed to try the level before the player passes it) or the same average difficulty (Each challenge is as difficult on average as one in the bigger level.) If the second the level becomes much easier to do, if the first an individual challenge must become far more difficult.