Do you intend to make the game Xbox controller compatible?
Also, third person does have disadvantages too. I would say that first person is certainly more responsive and immersive. Also, it's less exploitable. In reality, peripheral vision isn't going to let you know that someone is coming behind you. With the current viewing angle, you can see over walls, behind buildings, and around corners, which is a serious step back from the reality that Sui Generis is trying to achieve. Additionally, aiming a bow in third person sucks. It really does. The best you could do is center the camera angle directly over the shoulder and add crosshairs; yet another thing that messes up immersion.
The easiest fix for these problems seems to be to add a first person viewpoint. Is the lack of peripheral vision so terrible that we need the current omniscient view?