The point of direct negative is to minimize any chance of a bad connection causing brake failure in the worst of situations. Making a “good ground” for a 30a load is not as reliable as a direct connection to the battery. This isn’t a knowledge and skill thing, it’s eliminating the chance that the resistance stack up of frame welds, rust, wire fatigue, wire corrosion, greasy terminals, undersized factory electrics, high loads between the battery and the ground making a voltage divider, non-welded adhesive body joints, thin sheet metal, undersized hardware, and thermal expansion don’t cause failure in the worst of situations.

The auto-reset breaker’s point is to minimize the chance of total brake failure in the worst of situations. If you are worried about an unattended short draining your battery, then unplug the trailer when parked. Your electronics won’t get fried from this kit. It’s no different than leaving your lights on. Imagine a frayed wire causes an intermittent short as the trailer bounces. Would a 3 mile downhill run be the time you’d wish you could manually reset the breaker?

I’m not saying you’re going to die. I’m not saying you don’t know what you’re doing with wiring. I’m saying someone put in effort to make a reliable system with liability for manufacturing defects. These aren’t solutions for lazy people, it’s for minimizing risk