Multiattack as a bonus feat? Sounds good to me.
It looks like the vote's in favour of a bonus Multiattack then, which will boost its slam attack to +1.
The only thing we have left is flavour text and tactics. How about this for flavour text:
Chimpanzees are medium-sized apes that live in tight-knit troops with a distinct territory. Where two territories overlap, the troops may fight over the disputed ground. Each troop is dominated by the largest male.
These apes are unpredictable and dangerous animals. Chimps fight with their hands and teeth, but usually flee from danger into the trees. They sometimes ambush lone humans who trespass onto their territory and may attack small groups of humans on rare occasions, but are no threat to large parties. Intruders are often greeted with a “Smile” that exposes their long canines. This is a warning, not a friendly gesture.
Chimps are omnivorous, eating fruit, leaves, roots, insects, small game, bushpigs, and eggs. The larger jungle predators will kill straggling chimpanzees, but most avoid facing the whole troop.
Humans sometimes capture young chimps as pets. Playful and docile when young, adult chimps become aggressive and irritable. Chimpanzees are mature at eight years. Wild chimps rarely live over 40 years, but well cared for individuals can reach ages of over 60 years in captivity.
A typical chimpanzee is between 3 and 4 feet tall and weighs around 120 pounds. The largest males may approach 5’ tall and 175 lbs.
It's more or less the same as the original
Dungeon description, with some tweaking of the sizes to better fit with real-world chimps.
As for Tactics, I was thinking something like this:
Chimpanzees attack with a bite and two slam attacks, they often grapple their opponents.
These animals are disturbingly intelligent, and may use tricks or deception to distract their opponents. A troop of chimps co-operates in combat, and a band that is experienced with hunting together may even use primitive tactics, such as sneaking up to a foe from opposite sides to make flanking attacks, or having some of their number try to frighten weaker creatures to run into an ambush set by their companions.