Full Plot of the Cancelled Kashyyyk arc from Star Wars The Clone Wars: Season 7
Planet Kashyyyk is still neutral at this point in the war. Yoda travels to Kashyyyk, and his personal battalion is there waiting for him (they had been sent a couple of days earlier before the arrival of Master Yoda himself) and they inform Yoda that the Trandoshans have been doing deforestation in order to drive the Wookiees away to establish Separatists bases there.
The other reason is to intimidate the Wookiees into joining the Separatists or die off. Yoda senses Count Dooku behind this attack. It was the Wookiees themselves who called on the Republic for help, but being a neutral system – only Yoda and Clone Force 99 alongside Yoda’s personal battalion were sent there, with no additional clone reinforcements. Yodas battalion consists of 41st Scout Troopers and regular white clones with Yoda’s face slapped on their helmet.
As far as Chewbacca's role in this arc, we would have been shown his wife and family. Otherwise, the main Wookie Character is Tarfful. Other Wookies such as different tribes, elders, and children would have been shown as well.
Yoda wants to help the Wookiees so they get in contact with the few remaining villages that still live near a part of the forest which hasn’t been destroyed yet but that is about to be destroyed. Yoda advises them to leave their homes, but the Wookiees don’t want to.
The Trandoshans come with a massive force and they drive the Wookiees out forcibly alongside Yoda, who are thus forced to retreat deeper into the forest and up a river which leads them to a water stream. Yoda and the clones then suggest to bait the enemies following them into an area of the forest so they can drive them away from the Wookiee villages.
Echo, new to Clone Force 99, would have become a sort of super-soldier due to all of his bionic enhancements. He would fit right in with the Bad Batch, and his demeanor changed, since he was now more cold-blooded and composed, as opposed to the indecisiveness that he showed in previous seasons. He serves as a foreshadowing of what Anakin would become.
His lobot-attachment would have been used for communications since he has a communicator close to his forehead, which shows him interfaces that were directly projected into his mind, so he would see them with his eyes but no one else around him would see them.
As for The Bad Batch, they were more accustomed to relating with the Wookiees than the regs. Hunter suggests bold strategies throughout the arc which the other clones weren’t really ok with since the followed more strict protocol. The Bad Batch also had their own hover boat, with their "clone force 99" symbol on it.
In Season 8, it was planned for The Bad Batch to execute Order 66, and they would have been treated as cold blooded assassins, a bane to Jedi. Though it likely wouldn’t have been shown on-screen. However, this arc is mostly to show the Bad Batch working with Yoda and the Wookies.
The clones suggest to burn all the trees down in that area of the forest in order to trap the enemy into their own nest. The Wookiees are against it but they then reluctantly agree that this is the best course of action and their only chance at success. They ask for forgiveness from the trees before doing this, and they then give the clones permission to do so.
Similar to the Bad Batch episode in Season 2, there are Kinrath and Maylyas deeper in the forest, and the elements of Wookies being one with nature is similar to how Yoda, a Jedi, believes in the force. The Bad Batch don't understand it, but they go along with it.
As for the Trandoshans, their leader, Babwa Venomor, was working with the Separatists, for Count Dooku. Some Trandoshans would have had night-vision goggles and snail tanks that they could use to tear through the forest.
The fires manage to slow the Trandoshans down for a bit, but it turns out not to be a definitive solution. After escaping the enemy, Yoda and the Wookiees prepare for war. The Wookiees ask for the help of tree spirits. They venture deep into the jungle in order to go warn the other Wookiee clans that the Trandoshans are coming and to sway them not to join the Separatists.
They use what happened to the Wookiees following Yoda as a motivating factor to tell the others that if the Trandoshans were not stopped, they would soon be coming for them too. In the meantime, the Trandoshans are preparing for battle and they are shown to be very tribal with trophies of dead Wookiee heads nailed to the walls.
In the fourth episode, an all out war rages near the river because the Wookiees wanted to get far away from the trees in order not to harm their environment any further; and the battle ends up on a shore similar the one displayed in Revenge of the Sith.
Separatist craft land with Droid reinforcements, but the Trandoshans are the main enemy forces. One of the Wookies would have ripped off a Trandoshan's arms. Commander Gree and his forces would join the action with Yoda and the Bad Batch.
At the end of the battle, Babwa Venomor gets decapitated by Yoda in the same way Yoda kills Gree in ROTS, and he falls into the river along with his tank. When the battle is over, Kashyyyk agrees to allow the Republic to establish clone bases there, and became an ally of the Wookies, as they foresee a larger Droid Invasion coming in the future.
