Subject says it all.
On-Foot Camera Hook
http://pastebin.com/NMecvbyL
needs work. the player model doesn't move/rotate properly with the matrix/speed set in CamEnd() which might be un-needed(?). i'm also unsure if the camera's vRight does what it should.
Modified gravity hook to go with it
http://pastebin.com/ymWcnYWz
And of course you need to add GetGravity/Setgravity to CPed/CPedSA and a CVector in CPedSA to hold it.
Then there's the concern of the mechanisms of SA that deal with standing up on a surface after falling down, while doing any collisions, while rotating, etc. Here's my first crude and probably wrong attempt at it.
http://pastebin.com/pG44B15L
This doesn't deal with aiming rotations, and it doesn't deal with setting the Z position when SA thinks you're not standing on inclines/walls/etc. I have some research on the Z position if this discussion goes anywhere. Hopefully this will spark some interest.