He's always had power over the storms, unless Marvel changed the actual mythical character of Thor. The hammer was to increase his strength yeah, but Thor was always 'god of thunder.' As for sticking to the topic, I thought everyone basically agreed neither Juggernaut or Doomsday would do much damage to the other. Doomsday can't be killed the same way twice right? And Superman already beat him to death, so Juggernaut wouldn't be able to do that. He doesn't have any other powers to my knowledge. If that fight were to happen, surely Superman and the X-men would get involved and then everything would get all chaotic.