Becoming a werewolf shouldn't have to be a one time thing. There should be a repeatable option to speak to Companion members about redoing the ritual (assuming you cured your Lycanthropy). The only thing you do is drink the companion's blood, so you should be able to do it again if need be.
Then of course you can repeat the quest to cure it, when you want to. Then later on if you wish to become a wolf again, the option is there.

