The Toa used their power to crack open the spheres and wake the Matoran up. It didn't grant them all mini-super powers (The Matoran would have been a lot more adept for dealing with Rahi and Bohrak if that were true). Still, I like your answer because it makes more sense than just hand waving, and it and it is your story. So you win this round.
I could get into an argument about how the Turaga can only use their masks because of latent of the Toa powers still residing within them, but that will just make this ridiculous. Willing suspension of disbelief will have to suffice. Or it's just the rules of this universe.
Thanks anyway. *cough* cop out *cough*
Pffrt, hey. Don't forget, the reason the Mata-nui turaga are turaga to begin with is because they gave said toa power to these matoran, correct?