Here's what really happens when you block people from withdrawing immediately and use average price for withdrawals:

1. When price rises, people are dis-incentivized to withdraw money, because the average will be below the market price
2. When price begins to fall, the average is always above the market price, so people have an incentive to withdraw. Even more, because the withdrawal isn't instantaneous, people are forced to power down over time and sell all the steem in the process. This puts long term downward pressure on the price.

What you get is increased upward volatility and never ending downward price spirals

I'm all for abolishing all those silly limitations and letting the market rule