Since is a Lego anniversary set, it should be system base. Having said that, I would love to see a system set BIONICLE, understanding it would only be one set and not a G3 series, something similar to this or what Sokoda did:
I would love to have some great BIONICLE minifig, and if they add a Great Spirit Robot, it would be the cherry on the cake.
The logical option would be the 90th anniversary set have a yellow minifig with a Emmet face, which BIONICLE wouldn’t have, but a man can dream.