With the latest changes, the brahmin carts are even more useless. The original idea had them as the vehicle with the biggest trunk (exception the truck that was added later... which requires the most fuel instead, though), in the same time it was the slowest vehicle. Now it's slow and you can pack all your stuff into any other vehicle, so why should I chose a brahmin cart?
Btw. Disableing the group leader charisma check for car traveling makes not much sense / is pretty weak, imo. I can't take 8 people with me, because my charisma is not high enough, but as soon as I have a car with 8 slots, it is possible? Why? Did the car changed my charisma?
I would set the maximum amount of allowed car-followers based on the guy in the group who has the highest charisma, not the leader of the group (because "in real" the leader isn't always the driver).