Re: Seiza by ranks?
In our dojo, there is no order that we sit in. However, since I normally start out Ukeing for Sensei, I sit far right so as to not take a seat where the view is good if I'm not going to be using it anyways. When doing line techniques, it's normally the two highest ranking people first in line to demonstrate the proper uke and ukemi technique for the next people.
I can't image having 30+ people trying to figure out how to line up. We also tend to try to train with everyone. There's a LOT to be learned by experienced people training with beginners. Those people who attack you on the street are beginners, so if your Aikido does not work on the new people in the dojo, it wont work in the real world either.