The concept is to create a visual indication that you've "sniffed" enough before calling CQ. This would help remind people to sniff before CQing and give an indication when there should have been traffic that could be heard to avoid CQing too quickly. This might help with instances of stations calling CQ on slots that are in use.
There's lots of ways to implement this including turning the Call CQ button green from purple, and a countdown timer.
I wouldn't suggest something that enforces a sniffing duration because sometimes you want to check the slot for a longer period if you think you might have heard something. Also, change STEP #3 to "Call CQ if nothing heard"
Great idea. I Implemented it and it will be out in V8.7