Stephen,
I suppose I have a "maximalist position" on the meaning of "this Torah" in Dt. 31 (i.e., at least Deuteronomy, more or less) and you have an extreme "minimalist" one (i.e., Ten Commandments only), while the Mishnah takes a somewhat broader position, as this link mentions.
http://thetorah.com/hakhel-ceremony/
"It is unclear exactly to what “this Teaching (התורה הזאת)” (v. 11) refers. Mishnah Sotah 7:8 suggests a minimalist reading, that it refers to selected sections of Deuteronomy (1:1-6:3; 6:4-9; 11:13-21; 14:22-29; 26:12-15; 17:14-20; 28). Jeffrey Tigay, professor emeritus of Bible from University of Pennsylvania takes a more maximalist position. He argues that the entire book of Deuteronomy may be the referent, noting that, “[a]ll of Deuteronomy can be read aloud in three to four hours” (JPS Commentary on Deut. ad loc., p. 292), and, therefore, can still be read in one day as suggested in Deut 31."
http://www.sefaria.org/Mishnah_Sotah.7. ... arLang=all
Also in favor of a broader meaning is 2 Kings 23:1-2:
"Then the king called together all the elders of Judah and Jerusalem. He went up to the temple of the Lord with the people of Judah, the inhabitants of Jerusalem, the priests and the prophets—all the people from the least to the greatest. He read in their hearing all the words of the Book of the Covenant, which had been found in the temple of the Lord."
Note the reference to "all the people from the least to the greatest." As the link above points out:
"Verse 12 [in Dt. 31] is very clear about who must participate in the hakhel ritual: “Gather the people — men, women, children, and the strangers in your communities.” This verse offers a clear definition of העם, “the people” or “the nation,” that is very inclusive. It is much broader than the description of the same group in the unit preceding the revelation at Sinai in Exodus 19, where women are likely excluded, or at best, included via their fathers or husbands."
And regarding Ezra's reading of all of the Torah in Neh. 8 the link says:
"it is significant to note that in v. 2 the congregation is defined as, “men and women and all who could listen with understanding”; similarly the next verse notes that the text was read “to the men and the women and those who could understand.” Nehemiah uses the term “kahal” rather than “‘am,” and his congregation/nation, like that of Deuteronomy, but unlike that of Exodus, includes women."