If you're taking a look at roll-off time and do some changes with it, could you also take code from EQ which turns unit inside the factory towards its current waypoint?
For example: if you had factory send units to the right, you'll have unit get build towards right side. Currently if you change that direction to left, the unit would have to rotate on its spot itself freezing the construction. EQ changed that the way unit gets rotated instantly and can move right away.