If memory serves, Makoto also created/produced Coconuts Musume.
Taisei was actually IN Cubic Cross as the keyboardist, and I believe he was also their producer.
Hatake has written the music for some H!P songs, such as Goto's Yokohama Shinkirou and v-u-den's Koi no Nukegara.
But yeah, Tsunku's always been their frontman and reason-for-having-a-job.