Proposal in 2 part: Passive and Scripted.
Passive proposal:
Avatar hitbox shape does not change based on any given avatar action. At the very least, the height of the hitbox should be reduced while in the crouching or crouch-walking animation state. In a previous system I had developed, this was accomplished by cutting the avatar's height by roughly 40%. Though ideally, the top of the hitbox should be here the person's camera is located at all times while they are in first person so things such as prone animations can more accurately reflect the avatar's hitbox size.
Recommended to include a region setting for this, ie. avatar_hitbox_crouching
Scripted proposal:
Allows a script to effectively adjust the size of the avatar hitbox while worn via a vector. The avatar's physics interactions would be based on this size and it would disable the Passive hitbox scaling system while active. This will allow the use of larger avatars (giants), avatar-attached mechanized units, etc without the new for a separate physical object to properly represent their hitbox. The appeal being to allow the creation of full 1-to-1 avatar controls without the issue of your hitbox being confined to a tiny space between your legs. This function should be restricted to scripts worn by the person affected and should require permissions, ie. PERMISSION_ADJUST_HITBOX. The avatar's camera position should be moved towards the top of their hitbox whenever z-scaling is adjusted.
Recommended to include a region setting for this, ie. avatar_hitbox_scripted