I think race leader should start immediately after the safety car enters pit lane. And the other racers can overtake before start line.
Imagine, race leader driving 20kph to the start line, all drivers going one after one, race leader crosses the start line and he is going full throttle when drivers for example from 25-32 positions will have to go 20kph to the start line. I wouldn't be happy if would be at the end of the grid.
By the way, you change rules so often, its not good for a league.