I thought about this when you first posted, and tried again just now, but couldn't do it either time. My problem is that there are too many ways of being a good teacher, even for beginners. My father tells a story about the two teachers he remembers best from college. One taught him most of the statistics he still uses, but was dry and boring as a doornail. The other was exciting and inspiring and taught him to really appreciate the beauty of his field, but was at least 20 years out of date and often simply wrong. Is a teacher who imparts excellent basics better than one who inspires students to commit to really learning Aikido? Is one who is patient but overly flashy better or worse than one who can stay focused on a beginner curriculum but is a little impatient and angry with the students? A lot of that will depend on the student, won't it? Some students like to be challenged and confused, especially if they have a good, patient guide teaching the class. Others like structure and feel challenged to perfect their technique by the teacher's impatience.
As a sempai, I prefer beginners coming up through the ranks who have learned to be gentle, to practice safely, to appreciate and express an accepting attitude towards their own Aikido and that of others, to be more interested in their own learning process than in judging or teaching others. I think that makes the dojo a fun place to practice, and I think that those things are harder to learn later on. If I was running a dojo with lots of yudansha who all wanted to teach the beginners class, those would be the qualities I'd look for.