Hum, i suppose you're right. So i could go Nature's Warrior 4/Fist of the Forest 1 - Arguably this would make it the best choice.
That's a good choice. But the duration of the campaign should be a factor. You're assuming you're going to go all the way to level 20, and then stay there long enough to have fun with 9th level spells. If the game stops at 17, you might only have 7th level spells. If the game lasts until 25, you'll have a lot more build choices. Remember that the party wizard and cleric will often be two entire spell levels ahead of you.
MoMF is nice, but i'm only getting Humanoid/Monstrous Humanoid/Giant shapes. How huge is this? I'm not sure.
Expanding from just animals and elementals to three new types can be really good. Humanoid doesn't give you a lot of power, but it's good for non-combat situations. Monstrous Humanoid has a ton of good forms, and giants are much better than large and huge animals, because you can wear all your equipment (with wilding clasps). And don't underestimate being able to speak in wild shape - and automatically knowing the language of any form you turn into.
Also, Nature's Warrior advances the wild shape abilities of prestige classes. Some DMs interpret this to mean that you get all the "wild shape" (but not the "shifter") MoMF powers. If your DM agrees with that interpretation, you can try MoMF2/NW2, to sneak in one more type of creature (Fey?)
But the reach on Warshaper is just so damn good, and it's SUPER easy to qualify, doesn't even require a feat, the immunities are just icing on the cake.
The reach is nice, but if you're mainly turning into large and huge forms that already have good reach, it won't matter as much. I guess it gets really good when you're in a tiny form, or when you shapechange (yes, warshaper abilities work with the polymorph line!) into a fine creature -- you can be a mosquito who can attack from five feet away!
I like the Warshaper immunities more, and the +4 unnamed bonus to str and con. This gives you +2 to hit (or power attack), and, if you have a level of Fist, +2 to AC. The best thing about Warshaper is the +1 natural weapon size. Combine that with Fist, a monk's belt and Improved Natural Weapon, and you have good unarmed attacks that are two sizes larger. Get the wizard to cast Greater Mighty Wallop on you, and you're seven sizes larger! Now your mosquito with 5' reach can do gargantuan damage with a monk's unarmed strike!
Finally, fist of the forest. Gives me arguably more damage than Nature's Warrior because of damage dice advancement, and combo's awesomely with Bite of X + Shapechange.
That damage is nice if you're going to take levels of Warshaper or Monk, or go for all three Fist levels. Alone, it's only marginally better than the standard natural weapons of your forms. The real benefits of Fist are the ridiculous AC bonus and the +1 BaB.
