Re: Sempai/Kohai Relationship in Aikido
I'll second Janet's answer. I think it just comes down the the (rather obvious) point that we are not Japanese, especially old fashioned Japanese. My teacher is visiting my dojo right now. On the mat, she is vastly senior to me and very clearly 'Sensei.' Outside of the dojo we can go to dinner, see a movie, or whatever, as social equals and friends because that's how we do things here (in the US, anyway). That would never work in Japan.
So I think the same thing goes for sempai/kohai. In the dojo I expect my senior students to help the more junior ones (and they do!) and so on. Outside of the dojo we are a collection of people with widely varied backgrounds, jobs, and experiences - and no hierarchical relationship. Applying the dojo seniority structure outside the dojo makes no sense in our culture.
What I do like to see extend beyond the walls of the dojo is a sense of community. We are all drawn together by our common interest in aikido and hopefully our lives are enriched by knowing each other.