Proposed resolution:

This wording is relative to N5001.

1. Modify [exec.awaitable] as indicated:

   -5- Let with-await-transform be the exposition-only class template:

   
   namespace std::execution {
     template<class T, class Promise>
       concept has-as-awaitable =                                  // exposition only
         requires (T&& t, Promise& p) {
           { std::forward<T>(t).as_awaitable(p) } -> is-awaitable<Promise&>;
         };
   
     template<class Derived>
       struct with-await-transform {                               // exposition only
         template<class T>
           T&& await_transform(T&& value) noexcept {
             return std::forward<T>(value);
           }
   
         template<has-as-awaitable<Derived> T>
           decltype(auto)auto await_transform(T&& value)
             noexcept(noexcept(std::forward<T>(value).as_awaitable(declval<Derived&>())))
           -> decltype(std::forward<T>(value).as_awaitable(declval<Derived&>())) {
             return std::forward<T>(value).as_awaitable(static_cast<Derived&>(*this));
           }
       };
   }