Yes that's a fairly good point and I don't know any easy way around it either. Looking in the world of business, government, politics etc etc. would be a matter of fairly subjective ideas about moral goodness.

I suppose you could formulate an approach along the lines of experimental psychology, where you could deliberately design experiments with clearcut good/bad group outcomes. So get a bunch of people to be leaders in an experiment where their goal was to minimise their group members (including themselves) getting hit in the head with something unpleasant, build-in some selfish vs unselfish options, and then look at the correlations between leadership behaviours and oxytocin or whatever else you wanted to measure as an input. With a robust range of experiments you could perhaps develop something broadly useful.