I'm glad you had fun with it, TN, and thanks for the compliments.
One point of elaboration about Dupe Boy. If he hadn't been so all-powerful, the Lallors may have become regular characters throughout Adventure and even Superboy, and thus perhaps in mid or later Adventure, Shooter may have rewrit the # 315 plot - Subs tryout test and winner joins legion - with the Lallors in a competition to join the Legion. I think it's more likely than not if Dupe Boy had instead been in the power-range of Ultra Boy (say a duping power but also some odd limitation or certain weakness approximating Jo's one-at-a-time qualification.)
I hope to continue my Turning Points pondering in a few days or so. Right now I'm preparing my Final Tally write-ups for Polls that are closing soon. I'll try to squeeze it in when I can.