If you want a bad management team, you have to look to her sister's career. Her last (literally) attempt to keep relevant was a mess and it was barely half of the attention that she expected to get. Poor misono.
http://avex.jp/misono/
Kumi has one of the best teams for sure, specially if we think of her name as a brand, releasing a lot of different things, from valentine's day gifts, to energy drinks.