There are a couple things I wanted to say around this topic.
First, why can't a new Bionicle be aimed at the general teen audience? I mean like you said Transformers Generations markets itself to that general age range and it does amazingly. I feel like Bionicle could easily have a story that could successfully click with teens.
Second, what if, and hear me out on this, what if they weren't action figures? But instead system sets with structures and vehicles like say Ninjago or Nexoknights. Maybe with some specialized minifigs like Hero Factory Invasion From Below. I know Bionicle has its roots in constraction, but its reasonable that the brand should make some necessary changes in order to be successful.
In my opinion, the most important thing the original Bionicle had was its story. The lore, characters, and world are what drew me, and many others in. As long as this new Bionicle has good and strong story with good characters, I'll be happy.