Oh boy. Before hand I will note that most of these will be link between each other, because thats how problems tend to be, always linked with each other in a glorious mess of things.
-Being hindered by the fact that the story revolves around selling the toys.
I know its Lego and that is their goal, but most of the time they are only trying to make stuf look cool for kids or sculpt the story so as you, the consumer, will buy their product toys. By it self is understandable why the company is doing that, its just hindering it from its full potential. There is so much you can expand with this concept of Robots, magic, nature that its a shame really.
Having no expanded universe besides the one given by One writer and Lego.
Greg is a good written, but he is not the only one out there. There are a lot of good writers that can flesh out different aspects of this world that Greg cant and in a way we never saw from this franchise. Im pointing to Star Wars as the best example because they made their EU so interesting and so great (shout out to the Thrawn trilogy), that most people would still to this day consider some major events in it canon.
Inconsistency between media.
I agree with this because, what we see as canon is from the books, comics, movies and trailers. With most of them not following any cohesion in terms of story telling, which basically made the story of Bionicle so convoluted in the first place. Having a stable EU is essential if we want this franchise to last longer than the next cancellation and not being "selling toys" dependent.
-(This is still up for debate as the G2 story has not come out yet).
Not doing a proper reboot of the story.
While most would say it was necessary to start from scratch I tend to disagree because of the fact that the story of the previous line could have still be considered and expanded upon...if this new story was link with it.
Time travel in fiction is always tricky to pull of, but if done properly is amazing. Same thing was done with numerous Terminator movies, and most resent, The Star Trek series. It made that, the previous story was still there, it still had meaning and significance, but it also was linked with the one we have now so that by the time you get to G2 you have this massive EU that you can keep adding too without having to tell the story of what a Toa is, or what a matoran/villager is (if they did let loose with the EU, shrug).
These are just some of them, more I will evaluate afterwards if interested.
I can not stress this enough, that we need a proper
Expanded Universe in order to make this franchise a long lasting one
solely outside of Lego marketing influence. Easier said than done with a
toyline from such a company like Lego.
Edited for Double Post -Nyran