I have in the past heard of 3rd. kyu's starting dojo's; MY question would be: At what point does a person draw the line? IOW; where in a person's development?
For myself; I have the odd combination of being a newcomer to Aikido but a highly experienced teacher. What I know; I can teach effectively; but as yet I don't know enough to effectively teach.
Honestly; I'm far too inexperienced in Aikido to even consider teaching it; however (and this is the reason for my answer) given the choice between starting my own dojo at a low level of ability and no Aikido at all; I'd choose the former; so long as it was allowed.