Theoretically, if a Turaga died and was sent to the Red Star, would their new body need to be on the same power level as when they died? I.E. could the spirit of a Turaga be placed inside a new Toa body, therefore reverting them back to a Toa?
No, because they give you a replica of the body you were in. They aren't going to build a Toa body for a Turaga.