Qatana

Modesty? What does a hakama cover that gi pants don't?
I love how aikido looks when done in a hakama, as a dancer I covet being able to look like that as I fly.However I also agree that one's ukemi should be good and solid, and their technique good enough that sensei doesn't have to see your knees all the time, which I imagine I will achieve sometime after reaching shodan.
I also am of the "visible colored belt"school, it helps to gauge one's response when training with unfamiliar partners.
Anyway my dojo waits till shodan but I'm sure that sensei would not object to me wearing one if I visited an ASU dojo, or other where it would be permitted for a mid-kyu to wear one. And if I ever get my Aaiki-Tango workshop off the ground and onto the mat, I intend to wear hakama as I will be the Teacher and I bloody well am going to Look like one!