I wouldn’t advise this. The laptop ships with a small 1mm thermal pad between the CPU and the heatplate. Removing this thermal pad and replacing with paste will not give enough distance between the conductive copper heatplate and the unprotected components underneath, potentially leading to a short.
If you want to lower the temperature, buy a better thermal pad (like the Gelid GP Extreme) or a 15x15x1mm copper shim instead.