"Autres choses" in plural would need an article: "d'autres choses", as the plural of "une autre chose", remembering that the regular plural indefinite article is "des", which becomes "de" in front of an adjective and is elided before a vowel.
Besides "voulait" and "voudrait" do not sound alike.
"autre chose" without an article is a set phrase. With time and repeated usage, many set phrases have lost their articles.
"D'autres choses" can only be used in plural, with d' elided from de, which replaces "des" in front of an adjective and which is the plural of "une".