Explore the switches also. There used to be a switch that enabled you to summon more than one cohort from the ordinary leadership feat, though you would have to rest in between.
The other point fascinates me. Last times I have tried, I couldn't summon a cohort with any of the new races added after PRC 2.2, and I didn't think anyone had worked on the leadership feat since then, but evidently someone has, or else one of the other changes somehow affected leadership. I'll have to take a look at it again.