Since D&D is still new, I have generally been in the mode of analyzing D&D rather than improving or expanding upon the rules. However, my wife insisted that I allow her to play a Sphinx character, so I came up with rules for doing so.
First, rules on how non-humanoid monsters work:
A Sphinx cannot use, wear, or activate magic items in the normal fashion. Instead, she must imprint the item. This takes 10 minutes, as if it were a ritual (but has no cost or chance of failing). Once the item is imprinted, the Sphinx can use the power of the item as if it were in the appropriate slot, and the item does not work for anyone else. At this point the location of the physical item no longer matters (the Sphinx can leave it at home in her treasure horde if she wants to). A Sphinx only has the normal number of slots; when an item is imprinted in a given slot, the Sphinx loses the imprint on the previous item in that slot.
Example: A Sphinx can imprint a magical amulet, and will gain the enhancement bonus and properties of the amulet, and can use the daily power of the amulet as with the normal rules. If the Sphinx imprints a different amulet, she gains the powers of the new amulet, she loses the powers of the old amulet, and the old amulet can now be used by someone else. The Sphinx can still imprint a head item, two rings, and any number of wondrous items and consumables (but see more below).
A Sphinx chooses what kind of armor her hide will act as; she must have the appropriate armor proficiency (in reality, the Sphinx just has different degrees of toughness and fighting mobility, but for game purposes this is equivalent to armor proficiency). The Sphinx is treated exactly as a humanoid wearing armor of this type, and she has one armor slot which can be imprinted. The choice of which armor type to emulate can be changed only between levels. The Sphinx can only imprint armor of the type she is currently emulating.
Example: A Sphinx Cleric can emulate chain armor, and then has a +6 AC bonus, a -1 speed penalty, a -1 penalty to physical skills. She cannot emulate scale armor unless she takes the feat Armor Proficiency (Scale).
The Sphinx must choose what is being held in her two “item wielding” slots; this choice can be changed after any short rest. A wielding slot can be used for a wielded implement or another item which requires a free hand to use; this allows the Sphinx to imprint an item of that type. A Sphinx with shield proficiency can use a wielding slot to gain the benefits and penalties of a shield of the appropriate type, and the Sphinx can then imprint a shield in that slot.
If a slot is not used for any other purpose, it can be used for melee combat. A Sphinx must use at least one slot for this purpose. A Sphinx cannot use normal weapons, but automatically has proficiency with its natural weaponry, Sphinx claws. A Sphinx claw is treated as a Warhammer in combat, and can be imprinted with any magic weapon whose enchantment is valid for a hammer, and can use feats and powers meant for hammers. If a Sphinx has two free wielding slots, it is treated as if it were wielding a Warhammer in each hand, and had the Ranger ability to wield both at the same time. Each claw could then be imprinted separately, and the Sphinx could choose to take the two weapon fighting proficiencies. Alternately, the Sphinx can use both wielding slots for a “Sphinx rake”. This counts as a separate martial weapon which the Sphinx does not have automatic racial proficiency in. A Sphinx with the “rake” style can only imprint one weapon, but it counts as using a 2-handed weapon with d10 damage and a +3 proficiency bonus.
Example: A Sphinx wizard can choose “orb” in one wielding slot, and can then imprint a magic orb in that slot, and can use the orb implement mastery class feature. A Sphinx fighter can choose “melee” in one hand and “heavy shield” in the other, and can then imprint magic hammers in one slot and magic shields in the other. A Sphinx is somewhat limited, however, in that unlike a humanoid character she cannot choose “orb” in one slot and “shield” in the other, she must have at least one melee slot.
In addition, once per encounter, a Sphinx can use any imprinted magic item power which would normally require a free hand to use, such as a consumable or an extra wand. This power cannot be used if this Sphinx is using a slot to gain the benefits of a heavy shield, unless the Sphinx has the quick draw feat. Unlike a normal character, the Sphinx is otherwise rather limited in that it has no way to otherwise move magic items into or out of its virtual "hands", the only way to use a magic item power that requires a free hand is to choose it for a wielding slot or use this encounter power.
Example: The Sphinx can choose to use her imprinted Potion of Clarity. This costs a minor action, and consumes a healing surge as per the magic item description. The potion is now “used up” and this power is gone. The Sphinx won’t be able to use any other imprinted consumables in that combat (unless, before the combat, she chose “melee” and “Elixir of Dragon Breath” as her two wielding slots).
Wondrous Items which are purely physical in nature, rather than granting powers to the user, do not use the imprinting rule. They can be mentally commanded if that is specified in the description, but they cannot be imprinted and cannot be used if they really require hands. So a silent crowbar won’t be useful to a Sphinx and Pouches of Shared Acquisition are doubtful. However, a Golden Spade or a Skeleton Key can still be imprinted normally (the physical action is just a “special effect” of using the power).
Hmm, that took a while to write, I guess this is only part 1 of 2. And I would clearly need to write quite a bit more if I were writing this rule officially.