That's the same kind of marketing that failed during the Wii U days. The Wii Fit branding may still have some appeal, but it's more important for Nintendo to highlight what's new about this game, not to mention keeping the required peripherals to a minimum.
This same game as is would fail on Wii U as it would anything.
It's easier to bring back Wii Fit fans than to make regular gamers want to jump in into that in my opinion. In the end the appeal force is almost the same, the new feature of this game still appeals only for consumers that want a fitness app anyway, however as a new IP it fails to capitalise on a franchise continuity. The required peripherals would be the same, balance board would be optional. My family have one, I'd love to be able to keep using it without forcing anyone else to do the same.
Having worked at a games retailer during the Wii Fit and Wii U days, I can tell you that the kind of customers we're talking about strongly prefer everything they need to come in as few packages. Even if the activities with the balance board are only optional, this will confuse them as to whether or not they need the balance board, and will make them less likely to purchase.
I think that even for the Wii Fit fans, the new adventure mode is the main selling point. The more emphasis you put on that the better. The product has enough similarities to Wii Fit that fans of that will already understand it is a spiritual successor. The full Wii fit branding will confuse the message more than it helps.