And when I was typing a comment on it, an idea hit me. I think that if Lego brings back Bionicle as a system theme. The Constraction figures that may get added as a side set could be somewhat like this Mega Construx set. (Notice Atheon, not the Harpy or the Warlock.)
In other words, Kinda style them like the Mixels (The only system based constraction figures I can think of). If @DinosaursUnited’s theory is true, then making them a system based figure.
Another solution to this would be return Bionicle to a technic theme. If it was system, Bionicle would have to compete with the likes of Ninjago. If the theme was entirely made of Axalaras, Skopios, and Scout Trooper speeder bikes, it would compete against technic bulldozers. Obviously this means less sets per wave, but still.
Additionally, because the set would be priced higher, and have more pieces, it would be conceivable to aim the story at an older fanbase.
Its the only way Bionicle G3 is gonna be a thing, otherwise its going to compete with the similar theme of Ninjago.
It could still be released even during Ninjagos time, but if its released when Ninjago is still at its popular stage, then it will flop like G2, if its released just as Ninjago is at the point of ending, then it may have a chance, only if its done with care.