Well, Marendar is designed to destroy Toa, not pacify them. If he can turn Toa into Turaga, he does so in order to kill them–which makes practical sense, but this doesn’t fit with your idea of “child-friendly” psuedo-death. Also, Bionicle is the last Lego theme that bothers with being kid-friendly, or need I remind you of how certain characters died?
It’s worth noting, though, that Greg had this to say about his own ideas for Marendar and what he might have done if given the chance to continue the serials. It’s compatible with your idea, but probably not meant to work with that.