Okay, before I go off, let me remind everyone that if we'd gotten a 2010 as epic as the ones you all are describing, then Bionicle would not have returned. Just bear that in mind.
As such, I would completely go ham in creating these. Why? Because we figure that this is it. Here we go.
The plot would go through a whole year, with three waves (humor me). The Mata Nui v. Makuta titan fight would commence in Wave One, and some of the Toa and MR inhabitants would escape with the villains to help combat them.
Wave One sets:
Small sets ($7-$10)
Canister sets ($12-$15) Bear in mind that Toa sized sets were cheaper back then.
Toa Pohatu Nuva
Toa Jaller ReIgnition (sort of like an upgraded version of the Inika)
Laser Rahkshi (Toa size, obviously)
Skrall Branar (anyone remember him? An officer in Tuma's army in the 9th graphic novel, I believe. Yeah, he gets beefed up)
Titan sets ($20-$50)
Helryx vs Vahki-nui
Mata Nui vs Makuta
Wave Two would feature Mata Nui's defeat. He manages to pull the moons of Bara Magna back, but his robot body is suffering greatly. As such, Mata Nui grabs onto Makuta and uses a last-ditch ability to fuse the arms, upper torsos and heads of the two robots together. A team of warriors must enter the MR and shut it down for good before Makuta can undo the fusion. To aid the heroes, Mata Nui uses the Ignika to resurrect some of the MU's most powerful warriors.
Toa Onua Nuva
Toa Kongu ReIgnition
Matoro, Toa of Life
Lhikan, Toa of Fire
The Mind of Teridax
Finally, Wave Three, right at Christmas time. The heroes have beaten Makuta, but they have yet to beat the one pulling the strings. The heroes face Velika and the Element Lords in a battle that will change the universe forever.
Toa Tahu Nuva
Toa Lewa Nuva
Toa Kopaka Nuva
Toa Gali Nuva
Toa Hahli Reignition
Fire and Ice Element Lords
Jungle and Rock Element Lords
Water and Sand Element Lords
Great Being Velika
Helryx and the Exo-Toa
Nuparu and Hewkii Blast Crawler
Artahka's Chariot (with Artahka, obviously)
I will leave it up to you to use your imaginations on what these would look like.