Do we need another brake system ??

Yes it's a good idea. But the doom and gloom about always being at fault and sued if you don't is all conjecture. Devil's advocate, I have yet to see any suit where the defendant's lack of a supplimental brake system in their MH cost them a case. You may very well be in your legal and physical limits and a lot would depend on the accident, if there was even an investigation and if it was even considered. Maybe having one prevents an accident from ever occurring. Hard to prove that. But again, yes it's a good idea. Given your weights and laws it might even be required. Err on the side of caution. But the sky is falling scenarios people always put on here about getting half a million for being rear ended is a lot conjecture. Perhaps I am not looking in the right spot, if someone can cite a case where it was won or lost based on this. But yes, you should consider one.