I personally don't see a problem with this, I mean Bionicle was a product of its time and G2 showed all to well that this is true. If bionicle is to survive it needs to tackle a more modern relatable topic that kids will grab onto.
First and foremost, "In a time, before time" relative to what for all we know the G1 story could have been parralled with our timeline. Secondly you bring many compelling arguments here but what is it that say that our worlds issues and problems wouldn't be likely to happen elsewhere. I mean climate change is a natural thing but because of a sentient species aka humans it's becoming a bigger problem than it has ever been or will be. Now what is to say that another sentient species can't causes there planet to undergo simular effects of climat change of those currently on Earth.
What says it can't be mysterious and grand, some examples of things that come to mind is did their civilaization always look like this or is this the aftermath of a species undoing? What caused these drastic climate changes, was it ignorance or by accident? And so forth, tying fictional stories to real life things doesn't always hinder a good story keep in mind that G1 had lots of influences from Maori culture and other medias like comic books and sci fi. Even the original concept was pills that released warriors who fought diseases into the body. I also believe that G1 had alot to do with finding yourself and your place in the world hence the three virtues, characters such as Vakama and Matoro being central characters. Bionicle dealt with issues that was important to Faber back then considering he was taking medicine because of a brain tumor. Also I wouldn't have a hard time thinking he might had have to face these issues as well. Knowing full well that his life was on the line. Which also is a great parallel to the GSR dying in 06. My point is that original Bionicle dealt with things that was important to Faber back then and had several real world connections that created a story about realizing who you are, where you belong and fight for your beliefs until the end.
Again I can't see an issue with him using this as a thematical basis for a retelling of Bionicle. To further prove my point I would love to direct you to one of my favourite shows from my childhood and that's a Swedish show that aired during the summer called "Vintergatan 5a" (Milkyway 5a). The show was about 3 teens and a taxi driver going to space and landing on different planets to collect wildlife. Through out the series we are never told why they need to collect them until the last episode but before I touch on that let me tell you what the shows purpose was. The purpose of this show was to express existential questions that kids could understand and relate to and give them a broder perspective of life. So does the last episode fufill that goal absolutely let me tell you. The last episode begins with the crew returning from a planet called the dooms day planet. Which was ones a planet like ours with an civilaization about as advanced as ours that had wiped themselves out due to ignorance. Anyways the planet is now nothing more than a toxic and radioactive wasteland where it's inhabitants has turned into mutants. Anyways back to the plot in the previous episode we saw the gang that had been sent down to the planet trying to fight off the mutants from the vessel they where going to leave the planet with. The reason for their hurry was due to them activating a selfdestruct mechanism of the planet. Anyways they left the planet and escaped with one sneaky mutant that hitch a ride on their vessel but in the end it was the last piece of wildlife they needed. So afterwards their guide on this journey approperatly named Alien tells them what their mission was about and that had been to save Earth from a similar fate to the dooms day planet. As the planet explodes some of the casts reflects over what had just happened and in doing so not only conveying the series purpose to kids but also sending an enviromental message they hinted at earlier. The shows ends with them saving earth from all their problems as these mysterious creatures from another civilazation and then going back to their old lives. So what is my point here where to I want to get with this well the point I'm trying to make is that you can create a good story with an underlying message even with a modern topic such as climate change. Its an issue I think should be tackeled in even more childrens media because its one of our biggest issues and will probably be for another generation if not even more pressing for future generations.
Again climate change is a normal part of Earths functiong that's one reason why seasons exsist on Earth and that the weather and stuff changes. The problem is that we as a sentient species are using the planet against itself straining it and causing it to negatively effects itself. The reason I'm stressing sentient species so hard is because it doesn't natter if its humans, Aliens or biomechanical creatures who have caused these things to happen all of them are equally likely to cause those problems we humans currently faces. The Great Beings technically caused the destruction of their own planet due to not caring about wasting resources or caring about its inpact on the enviroment so even G1 tackeld this.
Great do so! I'm not gonna prove you wrong, I just wanted to broden your view about this topic. In the end its your call whether you'll like his bionicle retelling/Bionicle inspired story or not.