Somewhat late but better late than never, right?
In case someone else wanders here with the same question - this is possible if you use one of the programmable keyboards; many support simulating mouse movement via keys.
It's not as smooth as if game would implement it natively (like SH3 or 4). This usually works by you pressing or holding one of pre-programmed keys to switch to alternative "layer" in which you pre-program certain keys to simulate mouse (WASD or cursors for example). You also need to either press mouse button on actual mouse, or program one of the keys to simulate it because SH5 requires mouse to be pressed in order to move view around...
Those keyboards that allow mouse simulation typically ramp speed up as you hold mouse keys, they start slowly and then gradually speed is increased. Some keyboards also allow you to setup this ramp. Given these are usually high end mechanical keyboards (with corresponding price), you may want to check with manufacturer before purchasing. Also make sure the keyboard you're interested in actually supports mouse - not all do!
Anyhow, just my 2 cents, probably not everyone is aware of this possibility so hope it will be useful for someone...