If the Wii is capable of disc swapping, then I say go for it. However, I think Monster Rancher should stick to it's Sony roots. PS3 is the only one I know that can swap discs without going to the main menu. I like the promise of Monster Rancher on Wii. By that I mean you could further immerse yourself into training your monster personally. Say, do movements to instruct your monster to train in certain ways. Or pet him when he succeeds, or lightly slap him if he fails.
It can be make for any wii/xbox360/ps3 but i would love to see it on xbox360 and ps3 cause the wii conection have a lot of lag in some games and a monster rancher with lag would be a very anoying game.
Plus i would love to have a cross breed accion to breed one of my best monsters with one of my friend's best, and of course a real monster rancher tournament with people from world wide would be awesome too.