If this is indeed happening, I'm personally hoping for a reboot; retelling the story from the ground up so that it's accessible to new viewers, while hopefully fixing some of the issues from the original run and giving it a bit more coherence and (in my opinion, one of the most important things) character development. While it's very likely they'll use the new HF system, I would personally prefer a return to a more axle-oriented system with maybe some HF stuff to supplement it; I loved the old mechanical functions and would love to see them return.
I have a whole list of nitpicky things I would do, but I'll write that up when I have more time later. Short of it is that story-wise, I'd make it more mature, but without making it too 'dark and edgy'; just more... self-aware and presented with the proper gravitas. Set wise, I'd do what I mentioned already, but also with more challenging builds than either Bionicle G1 (let this be a thing) or HF gave us. Also, make Lime Green pieces not suck, and make Hahli's color scheme match her Mahri form as a Matoran. (No seriously, that color scheme was amazing!) If there are movies or (even better) a TV show, I'd prefer the more organic and less toy-like look of the first movie trilogy, but maybe with a bit more mechanical stuff thrown in as needed.