Use an ISO manager like this one: http://www.wiibackupmanager.co.uk/download/WiiBackupManager_Build78.html to make the ISO Into a wbfs format ROM which will split it into multiple files. I hope this makes sense.
I think Mewtwo is mid to low tier after a Smashfest last night but that's not accounting for balance patches andtech discovered in the future. And he's new.
In Pokemon, shiny pokemon are differently coloured pokemon. Lucario is primarily gold. The only shiny pokemon recolour they have in Smash is Mewtwo's green recolour (possibly Pikachu's red recolour in Brawl. They can be that subtle.)