There is of course nothing to stop us from continuing this. Suppose we have a one-quarter brain? Much more probable. One millionth? Even more probable. Maybe even single elements of a nerve cell? More probable still.

If the question is whether our conscious experience might be attributable to a Boltzmann thingy, the lower bound on the size of the thingy is the amount of brain it takes to be conscious. I haven't dissolved consciousness, of course, but I would be surprised if a single neuron could be conscious, no matter what state it was in.