...due to the press of time I did not code up exactly what you suggested, but instead used an existing range breakout system as a surrogate. The rules were:
1. NQ
2. Don't trade before 9:30 AM ET.
3. Long (short) when price goes above (below) a threshold
4. Hold 'til the close.
Whereas you talked about a threshold based on the average daily range of the market for some days lookback, this surrogate is equivalent to a 60 days lookback (the period I tested).
The best performance was for an NQ threshold of 25. It took 8 trades and cleared $738 for each contract. However, it is trading only late in the day. Setting the threshold lower to catch earlier trades loses money due to whipsaws. I did not try to optimize it, because my experience with breakout systems for a particular time period is the following. If you have to optimize it with stops, reverses, and takes in order to make it profitable, you're looking at too long a time frame.
I don't trade past 10:30, so I'm no expert, but my guess is that the random variations in the shape of the whole day make any kind of all day breakout system unsuitable.
Bets regards. - Mike