Check out Zelleqyllvan's Shifter details
here
Wisdom is your prime requisite for the Epic Shifter Shapes. Outsider Shape requires 25 Wisdom; Construct Shape requires 27 Wisdom; Dragon Shape requires 30 Wisdom.
With such high wisdom it is
cheezy useful to take at least one level of Monk to get the AC bonus. Take the monk level late in the build (level 37+) to max out hte Tumble skill for more AC bonus.
Shifting unequips your items. If you have a Wisdom increasing item you may lose bonus spells when shifting.
Depending on the shape you shift into the item and/or weapon properties your base form has may or may not apply to the shifted form. See the link above for details.
Beware the "dead shifter bug". When you die in shifted form you revert back to your base form but all your equipment properties no longer apply(ie. you +3 chainmail becomes +0) You have to unequip/re-equip each item or shift again for the properties to return.
I have a few Shifter builds if you have specific questions in mind.