You would have to find a way to cool the southbridge, and because of the graphics cards the area available is only 40x40x10mm. On the A8n sli delxue they used a horrible rubbishy little fan which was noisy and didn't cool very well, and thats why they started using heatpipes.
You can get a cooler that will fit in there, but it will be rubbish and noisy, and it seems a waste after you have paid for the heatpipes to remove them.
You would also somehow have to find a way to cool the voltage regulator.
If you wanted to watercool everything this would be fairly easy as you can get water blocks for the voltage regulators and the chipset.