Sorry but this sort of topic isn't allowed here, as it's basically a "what if", not really a theory. Canonically humans do not exist in either the Bionicle Core Dimension or any associated canon alternate timelines -- and canon is what we discuss here. Yes, it's possible LEGO could allow them to be added, just as it's also possible Bionicle could be restarted as a line about fluffy blue rabbits. That doesn't count as evidence in the sense of an S&T theory; as best it's just speculation, except here I think we all know it's not gonna happen.
Also, it would completely change the genre and a lot of people wouldn't like that, so it's highly unlikely they would do it just for the heck of it. If you like a story universe with both Bionicle-like things in it, plus humans, Hero Factory fills that role already, so no need anyways.
For those who do find it attractive, there is also always fan fiction.
And, for those reasons, topic will now be closed.