I think that, instead of Japanese CV, beginners should try Japanese CVVC as their first voicebank. While CV is super simple to record and oto, CVVC teaches concepts and skills similar to VCV, VCCV and arpasing. I'm not against CV voicebanks. In fact, I used to have zero interest in non-CV/VCV voicebanks until Xia Yu Yao came along. I just think CVVC is very useful for learning how to oto.
Edit: I cut down the length because I got too wordy...