ARCA already trades 04:00-20:00 ET. 04:00-07:00 is particularly illiquid - they haven't managed to grab the European business they had hoped. I expect that session will get dropped again.
I'd like a shorter trading day. 08:00-09:30, 09:30-16:00, 16:00-18:00 for starters. Most of the rest of the time is spent cruising ET, watching TV, falling asleep at the switch, etc.