What you are talking about is called "fanon", which means something that one or more fans make and say that other fans may use it (and this would basically have to be the "freeware" version like we do for the Expanded Multiverse, meaning you don't have to give specific credit when you use it).
One problem with trying to make a single fanon language is that nobody's going to agree to all the words. People like to have their own freedom to make up their own theories, etc. There's been a lot of interest in languages here lately. People might want to make a project like this. But I can't really officially sanction one, at least not without the admins' approval. Not really sure I'd want to anyways. I'd much rather leave Bionicle language where it is -- we have enough insight into it to be fun, and enough mystery to have room to make evidence-based theories about it. As soon as you decide you have to try to make the whole thing, it becomes just work, and not necessarily as fun, you know?
And more importantly, we require evidence-based theories here, other than approved projects. I have approved some projects that go a little ways into this before, along with some evidence-based theories, but that's not this topic, and I'm not going to be approving an all-out project at this time.
However, there's been a proposal, due to the strong interest, to have an official topic. I'm leaning towards having an official guide topic, which would be an optional place to post rather than the only. Either way, people would be free to try to get a bit more speculative in the replies in it, if it's made. Stay tuned -- this is not a final decision right now.
Regardless, I'm afraid this topic doesn't quite work. If you want to make a limited, evidence-based theory, however complex you want it to be, you may go ahead and post it as a new topic once you have enough of it made. Prior to that, this is more of a post-it-here. Just be aware that not everyone will accept an all-out language they'd have to work to learn, so I would strongly advise against trying. As TheSkeletonMan points out, we already have English "translations" to suffice where we have no evidence for the rest. That's good enough for the canon, and me.
Also note: there's more than one language in Bionicle, so you'd have to make Matoran, Agori (which Matoran was based on), Visorak, and who knows what else. IMO it's just not worth it.
So, thanks for the suggestion, but topic closed.