I'm not sure how effective a kingmaker Ozawa can be.
His group (in fact there are two, the Isshinkai and the Hokushinkai, may be the largest and since this time local party chapters/members won't have a vote, the strength of Ozawa and Hatoyama's combined groups is relatively bigger than last time. That being said, Ozawa has one problem the major LDP factions of old, i.e. until the 1990s, did not have. They also served as a means to educate and groom political heirs. Kishi handed the reins of his faction to Fukuda who handed them to Abe. Tanaka had groomed Takeshita (despite their famous falling out), etc. Moreover, the big factions always had often multiple potential successors in waiting, e.g. the Takeshita faction's 7-bugyou or the Abe faction shitennou, etc.

Probably because of his kowashiya activities in the 1990s, Ozawa has been unable or unwilling to groom any heir apparent. Former close associates like Fujii or Nikai have long deserted him or taken their distance.
Despite their famous falling out, Ozawa in a desperate attempt to field a candidate unsuccessfully even reached out to the former a few days ago. The majority of his (top) lieutenants (Matsuki, Suzuki, etc.) lack experience (particularly in Cabinet and high-level party positions) and have close to no name recognition.
Despite the existence of his Ozawa-juku, he has apparently been unwilling to teach his election magic to anybody else. Now, he has to choose between Kano (who has never been close to him), two members of the Hatoyama group (Kaieda and Ozawa) and the inexperienced Mabuchi. Not an ideal situation when you are going against Maehara who, despite his less than impressive term as party president in 2006, is still the people's most popular choice for PM and popular among many in the party because he could serve as a senkyo no kao during the next election campaign.

Best,
Chris

Chris Winkler
German Institute for Japanese Studies (DIJ) Tokyo