FYI, I have a library `wrapped` that provides essentially the same thing that's added here, but generalized to arbitrary "underlying" classes with a phantom tag, rather than only for `Generic{1}`: https://hackage.haskell.org/package/wrapped-0.1.0.1/docs/Data-Wrapped.html#t:Wrapped. This sort of thing shows up pretty frequently for classes other than just `Generic`, e.g. lots of instances can be derived from `IsList` or `Foldable`. In the class-tagged form, library authors can provide non-orphan instances not only if they define the _target_ class, but also if they define the _source_ class (e.g. `adjunctions` could provide `instance Representable f => Functor (Wrapped1 Representable f)`). I find this presentation reads more naturally, too: `data T = ... deriving (Semigroup, Monoid) via Wrapped Generic T`. Since a specialization is already being added to `base`, what do you think about including the more-general form, too? I think it'd be great to have things like `Applicative f => Functor (Wrapped1 Applicative f)`, `Traversable f => Foldable (Wrapped1 Traversable f)`, `Foldable1 f => Foldable (Wrapped1 Foldable1 f)`, `(Applicative f, Monoid a) => Monoid (Wrapped1 Applicative f a)`, and `Ord a => Eq (Wrapped Ord a)` all available for DerivingVia without any need for orphan instances. I've already documented some drawbacks and limitations of this technique (including some related to the Monoid instance specifically) in the library's [README](https://github.com/google/hs-wrapped#caveats).