I would like to point out that the South American people also knew about the wheel but never put it into use because of the terrain making it impractical(steep hills & mountains). The same could be said about the loose sand and a thin width wheel w/heavy weight, seems that it would sink into the sand too easily. Also on the sled and runners why couldn't the sleds be used to bring blocks from the quarry to the site(possibly more than one block at a time) and the runners used to take blocks the rest of the way. Especially if it did not take as many people to move them, this would help out the theory in regards of too many people up top with limited space.Removing the runners once you got the block close except bottom one and then pulling the block to position on last runner. When you had it to the final place just reverse ropes over top and with a lever on back side, tilt the block foward and slide off of last runner,possibly using lubricant under stone to help final alignment. Last thought here, as for the two workers in the picture using block for brake, why couldn't they run two ropes across the end of the block(while lashing on runners) to create a "plus design" in the center then with either a hoop made of wood or even metal tied to this center point run another rope down and behind block just enough to clear runners and then attach the braking block to it. The block would be minimal weight and always in perfect position to stop downward travel in case of accident or need of repositioning as stated above, plus freeing up a couple of workers which if they were moving the blocks with that few of men equals up to more blocks per same time frame. Just throwing these out there to fuel the fire!
(lobo for short)