Proposed resolution:

This wording is relative to N4950.

1. Modify [expected.void.obs] as indicated:

   constexpr void value() const &;
   

   -?- Mandates: is_copy_constructible_v<E> is true.

   -3- Throws: bad_expected_access(error()) if has_value() is false.

   constexpr void value() &&;
   

   -?- Mandates: is_copy_constructible_v<E> is true and is_move_constructible_v<E> is true.

   -4- Throws: bad_expected_access(std::move(error())) if has_value() is false.