Huh. Lots of answers to this question of development.
The opinions are swirling like flies on a hot turd.
My upbringing as a tree worker was in an educational setting, a 4yr college with a student work program. Our focus was on safety awareness, building skills, and learning about trees and how to care for them. Zero production pressure, no money involved.
My current co-crew leader never had formal training, started by free-climbing, and made mistakes that others died from. Completely self taught.
We pretty much share the same outlook, capabilities, and productivity, despite our points of origin.
Im not so sure if its even worth discussing the traits needed to be a "good arbo/climber." Or even what that means.
The topic that really interests me is the sharing of knowledge and the process of growth that occurs in those that choose this path. I think it is telling that the conversation drifted to what the apprentice must be like and do, rather than how we can help them learn.
I 2nd the importance of communication (with sena or without) as crucial to educating crewmates. Storytelling is the best suppliment to job experience, because if someone can learn from your mistakes without repeating them, you are doing good.