Can I patent this? It's an idea for a business?
Yes, the faceshield is a common replacement part. Most manufacturers offer various shades, including the original clear. The hinge hardware (some call them pods) are also available. Note that this is for most modern helmets. I can no longer find parts for my Fulmer (circa 1982). While Nolan has many parts available, I couldn't get a shield for my N25. (Also out of date - I no longer have it).
Safety slugs are designed to fragment rapidly and pose little threat of a ricochet. They generally do not penetrate very well, but create multiple wound channels. More effective? At What? If I were in an airplane, they'd be my round of choice. Same if I were in a school full of children I was tasked to defend. In normal circumstances I would prefer the hollow point if those were my only options. They're not though. I generally carry a soft lead semi-wadcutter for a bit more penetration, even through winter garb. If you can place your rounds accurately, under stress, then all of this is academic. A well placed shot from a .22lr beats a miss with a .45, everyday of the week. Concern yourself more with your technique, and basic skills. You are the most important factor in a gunfight.