All manufacturers extend the arc welding warning on modern cars.
One thing I absolutely wouldn't do is remove the battery cables. The battery acts as a dampener to transient voltages. It sucks up all high and low voltages. The biggest problem is that the battery is not hooked to many things with the key off. You still need the battery to establish ground though.
We use a device thats been out for about ten years. It clamps to the positive and negative terminals and guarantees to protect all electronics against arc welding. I have always presumed it to be a large capacitor.
Bosch Master, ASE Master, L1
33 years MB technician