The concept is very good. Using a harpoon instead of hands (handpoon?) was clever way around the model´s lack of hands.
From the beggining, it immediatly gives the feeling you are about to be attacked by wave of enemies, being intuitive is always a good thing in these kind of games.
If you can make the harpoon work, it seems quite promising.
And maybe change the gravity or the mass of the harpoon. its kinda strange to go from running at zombies like crazy to wait a few seconds until the harpoon reaches the statue.
And maybe change to a first person point of view while aiming.