Maybe I'm missing something here, but this would just be to clamp the heatsink to the CPU, yes? In that case you would run into the same problem that TIM was created to solve all over again. Ideally TIM would never be used, and both the heatspreader on the CPU and the bottom of the heatsink would be perfectly atomically flat with absolutely no space inbetween them. Because this isn't feasible, we try and fill the inevitable empty space with the most conductive stuff we can get. Using a different method of attaching the heatsink wouldn't solve that problem.