Recommended exterior protection accessories for a new BMW i4?

Man, i feel your pain. BMW moved to these water-based paints for eco reasons and unfortunately the hardness rating just isnt there anymore compared to the old solvent-based stuff. Those tiny chips are basically inevitable in Jersey without a physical barrier. Since you are on a budget and doing this in the driveway, definitely stay away from those cheap universal films. They are usually way too thin and turn yellow in six months. I would look into a high-quality pre-cut kit like the Xpel Ultimate Plus Paint Protection Film Pre-Cut Kit. It uses an 8 mil polyurethane which is thick enough to actually absorb the kinetic energy from road debris rather than just letting it pierce through to the primer. It has a self-healing top coat too so the light scratches from salt scrubbing basically disappear with a little heat. For the heavy salt issue, i would also throw some Gtechniq Crystal Serum Light Ceramic Coating 30ml over the film and the rest of the car. It wont stop rocks but the chemical resistance is what you need for that winter brine. Sadly $600 wont cover a pro shop, but you can get the partial hood and mirrors done yourself if you are patient with the slip solution.

I dealt with the same thing. I ended up applying a pre-cut film kit myself and its been working really well. Honestly so satisfied with the lack of chips on my hood now.