Ah, the Shapeshift variant druid. Despite the outcries to the contrary, I don't believe it's usable as-is. As a replacement for Wild Shape, it's weak. As a replacement for BOTH Wild Shape and the animal companion, it's downright criminal. Thus, after a bit of tinkering and such, I present to you the following modifications. Unless noted otherwise, all features are the same as that of the base Shapeshift variant. Feel free to take what you want and leave what you don't. Oh, and I apologize in advance for the length.
Predator Form
NEW - 1) Predator Form is now gained at 3rd level.
NEW - 2) At 6th level, you gain your choice of either...
A) the Trip (Ex) special ability while shifted (if the target is hit by your bite attack, you can make a trip attempt as a free action without making a touch attack or provoking an attack of opportunity, and the opponent cannot react to trip you if the trip fails)
B) an increase of your base land speed while shifted to 60 feet.
Once made, the choice is permanent.
Aerial Form
NEW - 1) Aerial Form becomes "Travel Form."
NEW - 2) At 5th level, you gain the ability to shift into the form of a flying, climbing, swimming, or burrowing creature (choose one). You traditionally take the form of an eagle or bat (flying), weasel or lizard (climbing), snake or caiman (swimming), or wolverine or badger (burrowing). You gain a primary natural attack, depending on the type of Travel form assumed: a bite that deals 1d6 damage (in climbing or swimming form), or a claw that deals 1d4 damage (in flying or burrowing form). Your size decreases by one category, and your reach becomes that of a long creature of your new size (0 feet if Tiny or Small, 5 feet if Medium). You gain a +2 enhancement bonus to Strength and a +2 enhancement bonus on Reflex saves, and your natural armor increases by +2. Your base land speed becomes 20 feet, and you also gain a new movement mode depending on the form assumed:
Flying: Fly 40 ft. (good maneuverability)
Climbing: Climb 30 ft.
Swimming: Swim 20 ft.
Burrowing: Burrow 10 ft.
Once made, your choice of Travel Form is permanent (but see the new feat below).
NEW - 3) At 7th level, you gain the equivalent of the Flyby Attack feat while shifted, though its benefit applies to the special movement gained by shifting.
NEW - 4) At 9th level, you gain a new special ability while shifted, depending on the Travel Form assumed:
Flying - Keen Eyesight (Ex): gain a +8 competence bonus on Spot checks.
Climbing - Perfect Balance (Ex): gain a +8 competence bonus on Balance checks.
Swimming - Hold Breath (Ex): you can hold your breath for (8 x Constitution score) rounds before you risk drowning.
Burrowing - Keen Hearing (Ex): gain a +8 competence bonus on Listen checks.
NEW - 5) At 11th level, you may assume a Travel Form of 2 size categories smaller than that of your normal form, gaining the following abilities (same as above unless noted): your primary natural attack's damage becomes 1d4 (bite) or 1d3 (claw), and your reach becomes that of a long creature of your new size (0 feet if Diminutive, Tiny, or Small); you lose your +2 enhancement bonus to Strength, but your enhancement bonus to Reflex saves increases to +4.
This ability enhances, but does not replace, your Travel Form (you may use either at your discretion).
NEW FEAT
VERSATILE TRAVEL FORM [General]
You are no longer restricted to a single form of travel.
Prerequisite: Travel Form.
Benefit: Choose one of the remaining Travel Form types that your don't know. You may now shift into that form in addition to that of your original choice.
Normal: You can only shift into a single type of Travel Form.
Special: This feat may be taken up to three times, each time granting an additional Travel Form type known.
Ferocious Slayer Form
NEW - 1) At 13th level, you gain your choice of either...
A) the Pounce (Ex) special ability while shifted (if you charge a foe, you can make a full attack at the end of the charge).
B) the Improved Grab (Ex) special ability while shifted (if you hit with a claw or bite attack, you can attempt to start a grapple as a free action without provoking an attack of opportunity).
Once made, the choice is permanent.
Forest Avenger Form
NEW - 1) At 17th level, you gain your choice of either...
A) the Double Damage Against Objects (Ex) special ability while shifted (you deal double damage to objects and structures when making a full attack).
B) an increase of your Damage Reduction while shifting to DR 10/slashing.
Once made, the choice is permanent.
Elemental Fury Form
NEW - 1) Instead of immunity to only the extra damage from critical hits, you gain immunity to both critical hits and sneak attacks.
NEW - 2) At 20th level, you gain additional elemental damage to your slam attacks while shifted, depending on the elemental form currently assumed. The amount of extra damage is the same as that of your base slam damage (i.e. 2d6 for a Medium druid shifted into Elemental Fury Form), and is comprised of the same energy as your current elemental form's immunity (electricy, acid, fire, or cold).