Hey there,
a few things IMO:
1) there was no need to seperate the limbs onto different layers - this is a waste of time
2) if you start with the limbs further appart, they will not influence eachother
3) you attached the arms to the main rig bone - i dont know why, if you rotate the body the arms won't move - the arms should be linked to the chest
i've never rigged the bottom of the body upside down like that, surely our movement stems from our attachment to the ground - so doing it this way means you will have to do a lot of extra animation to make your feet stay in place if you decide to move the hips? I didn't add this as a numbered point as it might have its advantages in certain situation.
Hope that's useful
