Assuming the racial is opt-in opt-out at-will, you’re essentially left with a system where the “want to be human druids/bri’ish rogues” will swap the curse option for the 3 days of every 29½ there’s a full moon to the current form. Or they won’t play. Those people will be, on average, 95% human.
You’ll see a decrease in the number of Worgen models out in the world with maybe an increase in the number of people picking Worgen the race. Is that really what you want? Does it serve what those people want, because then they have to go through extra steps to get a worse version of what they are actually pursuing.
I think it’s inclined to make the average “I like being a wolf” enjoyer and the average “I like being Bri’ish” fan both more unhappy and then also not meaningfully improve the situation for people who want to RP out the being-cursed part.