C++ parameter pack with single type enforced in arguments

I want to be able to do the following:

#include <array>
struct blah { };

template<typename... Args>
constexpr auto foo(Args&&... args)
{
    return std::array<blah, sizeof...(Args)>;
}

auto res = foo({}, {});

The following answers aren't satisfying: they just want to check that the parameter pack is of a single type, but I want to convert the values right to it in the arguments (else it does not work).

C++ parameter pack, constrained to have instances of a single type?

Parameter with non-deduced type after parameter pack

Specifying one type for all arguments passed to variadic function or variadic template function w/out using array, vector, structs, etc?

I also can't use initializer_list since I wouldn't be able to count the number of arguments to pass to the array type. And I especially don't want to type foo(blah{}, blah{});.

What are my possibilities ?