By "China," I am referring to the Mainland, Hong Kong, Macau and Taiwan collectively, without regard to geopolitics. Is there a word that refers to this entire region that would not offend any Mainlanders, Taiwanese or citizens of the Special Administrative Units?
maybe "大中華區". most multinational corporations used this term to describe the regions you mentioned.
such usage is correct, in context of nowadays, or recent decades. historically, taiwan was integrated into the chinese empire after ~1683. before that time, formosa was colonised by the dutch, spanish.
last, and most importantly is: how do you define "chinese speakers".
there're many ethnicities in "greater china" can speak chinese, they've their own cultures, languages and ideas of state / nation. so, "politically neutral" is, imo, unattainable.
it's better to seek a term that's vague, fuzzy enough; that no-one want to waste time and effort to argue its precise definition.