I'm not sure why Wookies would necessarily need to be innately intimidating. Consider this:
The representation of Intimidation in the rules is linked to Coerce and Willpower. Wookies don't inherently use Intimidation in their culture. Why not? Because they aren't concerned with such sophisticated methods of communication. They just get mad and cut to the chase.
1. They get mad easily, hence the low Willpower.
2. They have little use for Intimidation because that's like making a threat. Wookies don't waste time on making threats... they WILL pull your arms out of your sockets; hence the low Coerce.
3. Even in "A New Hope" when Chewbacca was playing R2 in chess, Chewie did not directly Coerce (Intimidate) anyone. Han did. Han was the one that created fear in 3P0. In fact, the only thing Chewie did was whine because R2 made a good move, "Crying about it won't help. It was a fair move." - 3P0 to Chewie.
4. In "ESB" when Chewie starts to strangle Lando. Did Chewie Coerce (Intimidate) Lando beforehand? No. Lando removed the binders from his wrists, and immediately, Chewie started to choke him... without warning.
5. Any time we ever see Chewie do anything remotely terrifying, it is always in the heat of battle. Any other time, he's a pretty chill dude who gets along with pretty much everyone.
In these scenarios, we can see how a character being afraid of a Wookie has nothing to do with the Wookie using Coerce. The character is innately afraid of the Wookie because he knows the Wookie will rip his head off in a fit of rage - which is linked to the Wookie's low Willpower. This isn't Coercion. It's just a fact of life.
Coercion is used as a conversation point. You're trying to bend the will of someone else to your liking. Wookies don't do this at all. Of course, it is fair to say that when a Wookie is in rage, it is very prone to causing fear to all witnessing parties. But that's balanced out in the nature of combat. If you aren't smart enough to figure out that you should run away from a 7'5", 400 lb death machine in the heat of battle... you're either too terrified to respond, or you want to die. Running away in this manner is still not Coercion, though. It is just a natural fear mechanic of battle.
You guys are seeing a flaw in the system, and all I see is something that makes perfect sense. Wookie is as Wookie does.
This is a very good discussion.
Several arguments, particularly this one ^, have made me think both that a low-willpower is appropriate for a wookiee, and that coercion aught to be based on willpower.
However, you still have the fact that wookies are both big and strong, and have a reputation for violence. This makes a wookiee potentially a great deal more frightening than the average member of most other species. As a GM, I would not feel like I was being unreasonable to give a boost die to a wookiee making coercion checks, depending on the situation at hand and how he was doing it. (A wookiee might also suffer setback dice when dealing with somebody who didn't understand Shiriwook) Likewise I might grant a boost die for another character making coercion checks involving the wookiee (i.e. Han intimidating C-3PO). Basically counting the wookiee as "the right tools for the job."