I wanna ask if is there a need to add the SHA512 Hash generator.
Depends on why you believe we would need it. Is it because of the funds' security? If that's so, we don't use SHA-256 in the final step, but RIPEMD-160 as told by mynonce above. I really can't think of another reason. SHA-256 is also used in mining, but that's probably not related.
Collision with 256 bits seems realistically impossible. Watch this for fun:
How secure is 256 bit security?As for the speed, SHA512 is faster to compute compared to SHA256 in modern hardware so there is no benefits there either.
Isn't speed a benefit? And not only speed, but computational expense.