yes the apparent weight of the aircraft would decrease but not by X/2 at half the rotate speed that you suggest. This is because even at rotate speed you still have some weight bearing down on the runway until you rotate which in turn increases the angle of attack of the wing which increases lift and lifts a/c into the air. On landing remember on airliners the spoilers come up and get rid of most of the lift over the wing, planting the a/c firmly on the ground. On light aircraft with no spoilers it can be a problem braking in slippery conditions because the aicraft is quite light after landing as you rightly suggest. Hope this has helped
