maybe "大中華區". most multinational corporations used this term term to describe the regions you mentioned.
such usage is correct, in context of recent decadesnowadays, or nowadaysrecent decades. historically, the same regions are parts oftaiwan 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.