Yeah, I was thinking the other day...doing a successful but less than perfect kotegaeshi on uke actually leaves you open for an arm bar when uke is on their back. I think thats why its vital we bend our knees and not hunch over...although I still hunch over
If the arm is in the center and the knees are bent then the arm would probably not be that vulnerable. Uke's legs would then be out of his sphere. Then there is a "nikkyo type pin" for uke's leg...Ouch!