I think older trainees should debut. I guess this is a matter of having a target though: I would 100% be interested in older (as age) groups, but there should be a high demand. I definitely don't like seeing so many 15-17 yo line up, I'm not interested in them most times, they are too young and without at least some 20 year old people to appeal to me more with a more adult attitude/image.
About age distribution, it depends. For example in Loona they debuted in 2018, Vivi was 22 year old in international age (96 liner) and Yeojin 16 (02 liner) but in the middle there were all the 97/99/00/01 liners so it feels a good balance. It depends.
