I was thinking along those lines as well, Beyond the Shores of Mata Nui(Story/History) talks about four major gods:
Artakha, God of Industry/Hard Working, Karzahni,God of Repair, Ekimu, God of Fortune, and Makuta, God of Retribution/Justice.
These Gods also have practical uses(pray to Artakha for hard working employees, pray to Karzahni that you will get better, pray to Ekimu for good fortune, and pray to Makuta to smite your enemies) Of course there would be tons of diverging lesser gods worshiped by the different Koros and stuff. There should probably also be gods of each of the Elements.