Grow your neurons out of your skull.
The cap would be a surgically bound equipment, with tubes inserted into the brain, and a mesh of artificial blood vessels, which circulate blood with neuro-trophic agent, to extend and grow neurons into the tubes, eventually reaching a broad compartment in the above cap.
The compartment would be modular and the tubes -- connectable wirelessly over the sections of the tube, so that when it's filled, the neurons can be attached to neural transponders at the sections of the tubes, to continue interact with the rest of the brain, and the new tubes can be drilled into the brain to continue the process with a new empty compartment.
The expected result is, that eventually, the surrounding mobile mass of the brain would constitute much larger part than the original consciousness, making it less painful to lose it.
I suppose, something readily doable, because it doesn't require deep drilling into the brain. Probably reaching the surface of the brain would be enough.