in halo you can see legs but with the camer fov and unture perspective it doent realy look all that impresive. i gess having the doom3 inverse kinetics to make the feet look like they are realy standing on the ground rather then just the ET floating player would go some way to help
with this you also need some way to acount for the way the head moves forward when looking down (in front of the chest) and back when looking up (behind the chest) otherwise you would end up looking though the center of you body
in q4 single player there are no shadows since they dont look to ralistic without player model but in multiplayer q4 they are. my gess is that players (unlike AI) could use your shadow to work out you position so if you cant see your own shadow it puts you at a disadvantage