Replace arrays of function pointers using templates in modern c++

I have some legacy code using arrays of function pointers in order to emulate memory handlers. So I'm now trying to have the same functionality using templates. Here's what I tried so far :

template <typename R, typename ...ARGS> using function = R(*)(ARGS...);
template<size_t Size> using ReadType    = function<SizedUInt<Size>, const uint32_t>;

// arrays to redeclare
std::array<ReadType<8>,   memory_handler_size> read_8_handler_;
std::array<ReadType<16>,  memory_handler_size> read_16_handler_;
std::array<ReadType<32>,  memory_handler_size> read_32_handler_;

template<size_t Size>
void initializeReadHandler(uint32_t begin,
                           uint32_t end,
                           ReadType<Size> func) {
    begin >>= 16;
    end >>= 16;
    for (uint32_t current = begin; current <= end; ++current) {
         //read_handler_[current & 0xFFFF] = func;
    }
}

How can I declare the read handler arrays in order to initialize them using the templated initializeReadHandler() function ?
I don't want to use std::function as I can't afford performance overhead ...

Thanks for reading me !