Well unless the wildshape acts differently here but maybe if you want to focus on forms and AB, perhaps you could take an AB class of your choice and take 12+ and gain wildshape and take plant shape (Treant and Shambling Mound) as a feat, the prerequisite for plant shape is 12+ druid levels.
To go for magical beasts that have celestial leopard, phase spider, or winter wolf. You would need 25+ Wisdom which is a heavy investment especially if you need to fight in your original form and not using spells.
Dragon shape needs 26 druid and 29 WIS which may not synergize with what your looking for.
All this information is taken from the stock wiki and it looks like the stats of the forms overwrite unless your proper form has a higher stat.
These are the stats I found on the wiki and perhaps this may give you an indication of what you want your primary stat to be.
Type of feat
Class
Prerequisite
Druid Level 12
Required for
None
Specifics
The character with this ability can take the shape of an plant creature. Available shapes include Treant and Shambling Mound.
Shambling Mound
STR 21
DEX 10
CON 17
2-12 base damage
20 Armor Class
Immunity to disease, critical hits, mind effects, paralysis, poison, fear.
Some damage resistance to lightning.
Treant
STR 29
DEX 8
CON 21
2-12 base damage
22 Armor Class
Immunity to disease, critical hits, mind effects, paralysis, poison, fear.
50% vulnerability to Fire.
The Red Dragon shape is the strongest of the three. The following stats are obtained from dragonform, -
STR 33 DEX 10 CON 23
2d8+1 damage
28 AC
150 temporary bonus hitpoints
+1 attack bonus
Immunity: Mind effects, Paralysis, Sneak attack
Spell Resistance 22
True Seeing
Racial type Dragon
The other wild shapes are here.
http://nwn2.wikia.com/wiki/Wild_shape Also mentioning that druid 16th level appears to be where elemental shapes are gained.
All this information is taken from the vanilla nwn2 wiki so I'm not sure what changes that have become commonplace here yet. So just to summarise..
Maybe taking 12-20 druid for the shapes, 20 druid would give all wildshapes and dire varients, Elemental shape and the elder versions and if you spend a feat on a druid level past 12th druid you can grab plant shape. The other classes maybe complimenting the AB progression your looking for.
Hope that helps and veterans please correct me if anything's changed from the information I given!
Edit: Build gurus, Does weapon focus and improved critical in unarmed strike work with these forms?
Another edit: I just remembered about intuitive attack which could synergize with the requirements in forms, details underneath..
Intuitive Attack
Type of Feat: General
Prerequisite: Base Attack Bonus +1.
Benefit: With a simple or natural weapon, you may use your Wisdom modifier instead of your Strength modifier on attack rolls. This bonus is applied when you equip/unequip a weapon or change shapes. This includes unarmed fighting.
Special: A fighter may select Intuitive Attack as one of his fighter bonus feats.
Use: Automatic. (This bonus is calculated and applied when you equip/unequip items)
If you have Weapon Finesse you will get the difference between your Wisdom and the higher of (Str or Dex). A 14 Str, 20 Dex, 30 Wis character with weapon finesse will get a +5 (30 Wis - 20 Dex) AB bonus. Without weapon finesse the bonus for the same character would be +8 (30 Wis - 14 Str).
<i>You fight by faith more than brute strength.</i>
Valid Weapons: Club, Dagger, Dart, Light Mace, Sickle, Spear, Morning Star, Light Crossbow, Heavy Crossbow, Quarterstaff, Sling, Silver Sword of Gith, and unarmed attacks.