Puer's D&D

Shape shifting

This section applies to all shape shifting, including polymorph, wildshaping, alter self, etc. In order to improve balance with 3rd edition rules, I recommend limiting the forms using the CR of the target. I suggest allowing a CR around caster level -2. This allows the forms to still be powerful, but insures that they should be weaker than the character's normal form. It could also be a check as the described below. As per normal 3rd edition rules, characters never gain the following from the target form:

hit points
base attack bonus
base saves
extraordinary abilities other than special attacks
supernatural abilities
spell-like abilities
mental ability scores
any templates
any atypical features (target always has average ability scores, coloration is always normal for the target form, etc)

Additionally, the character must be familiar with the form. Whether a character is familiar is entirely up to DM descretion, and the DM may choose to allow familiarity. A DM may choose to allow familiarity after a single encounter with a creature, or even from a detailed description in a book, or the DM may require some longer period of study of either a living or dead speciman lasting anywhere from hours to days. The DM could also require a Knowledge(nature) (or other appropriate) check before granting familiarity.

The form must be able to fit in the space available to the character (there can be no hostile creatures in the space, and non-hostile creatures must voluntarily move out of the space). Any items that could not be worn by the new form simply merge into the form and are inaccessible. Items that could be worn in the new form are worn appropriately.

Wildshape

Druids use the Spellcasting(polymorph) subschool skill to control the forms allowed. Also use some rule like the Concentration check above. The base DC is 20, modified as below:

+1 per CR of the target creature (minimum +1)
+2 per size difference (from the character's normal size, not their current size)
+6 per additional extraordinary ability gained (not including those normally gained) - requires appropriate feat
+10 per supernatural ability gained - requires appropriate feat
+0 for animal type
+6 for humanoid type - requires appropriate feat
+4 for giant type - requires appropriate feat
+6 for fey type - requires appropriate feat
+8 for plant type
+10 for elemental type - also gains targets all extraordinary and supernatural abilities if the target is a standard elemental
+10 for dragon type - requires appropriate feat
+3 to reduce the time from a standard action to a move action
+6 to reduce the time from a standard action to a swift action
-5 if you have at least 8 ranks in Spellcasting(druid)
+10 when using wildshape after having failed a wildshaping check since dawn (cumulative)
+10 when using wildshape after having taken 10 on a previous wildshape check since dawn (cumulative)

We could grant some free feats at certain levels, like a feat that allows 1 size difference for free, or allows one or more extraordinary abilities for free, or allows certain types, or decreases the DC in certain circumstances.

Here's the general rules to use for shape shifting.

Druids have Spellcasting(all) as a class skill already, so there is nothing extra needed there. Druids have a special class ability that allows them to polymorph without casting the Polymorph spell as normal. This is a supernatural effect.
Maintaining the shape requires a Concentration check once per hour to avoid unconsiously shifting back into the characters original shape. The check starts at the initial DC-5 and increases by 5 every hour. A character can voluntarily leave a shape at any time. Failing a Concentration check is not the same as failing a Wildshape check, it merely ends the effect.
A character that has failed the needed Concentration check feels their body begin to shift, and can choose to immediately try another Wildshape check of the original DC. If they succeed, they maintain their shape without shifting back. Failure is treated normally as a Wildshape check.
A character that goes unconcious does not immediately shift back, but they will automatically fail any Concentration check they need to make if they are unconcious at that time. A character who is only sleeping naturally can make their Wildshape check to maintain form, but any other cause of unconciousness (such as magic, poison, or hit point loss) does not allow that.