The 24 team leagues make it kind of tough to form rivalries. Against some opponents there are only 3 games, with just 6 games against most other non-divisional opponents. A team with an injury is really at a disadvantage in the season series against a non-divisional opponent.
It would be pretty easy to balance the schedule for an 8 team league with 2 divisions. Assuming that the 3 game series format remains, there would be 30 games against divisional teams and 18 games against non-divisional teams for a total of 162 games.
With all of those games against a handful of other managers, there would be a lot of good rivalries.