I'll second Opher on this one - most of the things oh your list is optional, few are required for a good teacher. They come in many flavours...
I'd like to try and split Yun's list on characteristics more needed to teach beginners, versus needed to teach advanced people.
* understanding of students' problems
* sense of humor
* clarity in physical demonstrations
* ability to teach one thing at a time
* desire to learn
* still a student him/herself
* many years of aikido/teaching experience
* real talent for aikido
Clarity in demonstration and or/verbal explanation is always a good thing, of course, but one of my favourite teachers had non of these talents. I do not think his best job would be to teach beginners. I like it when teachers take ukemi for everyone including beginners, but do not think this is necessary.
Then we could make another list of what is needed to teach children, which I think would look very different.