My point is that I want to offer the watchOS app for free.

In terms of functionality, there is hardly any overlap between the watchOS and iOS apps. The iOS app complements the watchOS app. (The app I am talking about is Ready Steady, see https://apps.apple.com/app/ready-steady/id1639942158?platform=appleWatch and http://readysteadyapp.com/).

I think, for your own sanity, you should release a paid-for iOS app that comes with the Watch app. Yes, this is exactly what I want to do. But what is the best way to implement it?