I would love to be able to offer 2fa in our Rails apps for the same cost as regular user management.

I have used https://github.com/tinfoil/devise-two-factor successfully in the past. It's good but it doesn't provide any UI for managing the second factor e.g. creating it, resetting it, allowing admins to manage it etc. so we would need to create all that.

We would probably need to spend some time figuring out the UX of all that first.