The best safety upgrade - your mindset while riding. Is it a safety upgrade of your GS500? You betcha'!
You don't need to have a "Holy Crap" moment to be a safe rider. In fact those moments only help if you learn something from it and change your riding accordingly. In fact your lack of "Holy Crap" moments is most likely telling you that you're doing it right so good for you. I've had a couple of those moments, but thankfully relativly few and I try to learn from them. Just don't get too relaxed and follow these tips. These are more or less in order of importance but that depends on different things:
1. Always wear a helmet (no brainer) and preferably decent gear, I'm no gear nazi but if you want to be safe.
2. Never expect a car to do the right thing. Give yourself an out, expect that oncoming car to turn left in front of you with no signal, expect the guy to change lanes into you.
3. Move through areas which limit your option as soon as possible, don't cruise in blind spots next to cars. Pass semis quickly, etc.
4. Intersections allow people to kill you from all four sides. Look before going through them even when green, be ready to dart in between cars/go in the ditch when someone is about to rear end you.
5. Pretend you're invisible, because you pretty much are.
6. Never ride beyond 70% or so of your ability, this gives you options to stop or swerve without crashing.
7. Watch the road surface, sand, gravel, oil, water, surface grooves, etc.
8. Be very careful in wooded areas, especially in turns, for wildlife darting out, they could ruin your whole day (theirs too)
9. Don't ride around closing time since everyone is drunk.
10. "Everyone on the road is a maniac, and is trying to kill you. Ride accordingly."
And remember that going down really sucks, but with decent gear you pretty much always live, usually without serious injury. It isn't until you hit something hard that it gets really bad; cars, deer, trees all will put a major hurt on you. Keep riding safe and avoid the holy crap moments.
A WORD ABOUT GEAR
True that it's your choice after all. It's your life, your body, your pain so to speak. Do as you please. If you don't like wearing gear, fine, just make sure you read how to treat road rash (abrasion) and be aware how it feels. Maybe you'll change your mind picturing a scene when you'll be glad you know that "Cuts that continue to bleed after 15 minutes of direct pressure, or cuts that extend deep into the skin and have edges that pull apart, may require stitches." and stuff like that. You may Google some pictures about motorcycle injuries to revisit your view on bike body protection.
We are into exciting, but dangerous sport. Admit it. And act accordingly. Will a hockey goalie step out onto the field without protective equipment? Will firemen go into fire without their gear? Accept the fact that we are in need of protection. Get it. Wear it. You'll thank yourself later.