It's never happened off of a proper triangle. Even if we ignore the fact that the guy would have to chew through his own arm first, that scenario still doesnt agree with anatomy. You know, unless your balls are somehow above your pelvic bone...
Someone grabbing your nuts is a possibility...vaguely. I mean, it'd be hard, but theoretically possible. Thankfully, I don't tend to get into streetfights while naked. If you do, you have a lot to reconsider about your lifestyle -- and it goes far beyond the realm of bjj. Because, you know, grabbing nuts through jeans (from that position especially) doesnt work as well as you might think.
Furthermore, if someone's in a tight triangle, he's going out in 5-10 seconds. Even if what you're suggesting is feasible, someone could endure some pain for that amount of time. Plus, cutting the angle and underhooking the leg or free arm will negate both slams and/or nut grabs.
As for guillotines, thumb in the ribs? Seriously? In adrenaline fueled scenarios, people have been known to not even notice getting stabbed... but those damn rib pokes! They instantaneously halt any action!
The other problem with all of this is that, again, a proper submission has someone passing out within seconds. An untrained guy, who's never been in this situation before, will almost always tweak out and just try to pull your arm or legs off of him. If you're in a solid guillotine (you know, the kind which you tap to in under 2 seconds), you won't have enough time to blindly find someone's eyes or cause enough pain with your thumb or whatever.
While I do agree with you that anything can happen and training -- or even being an accomplished pro -- doesn't make you invincible in a street fight, most of the scenarios you've listed fall soundly into the 'lol no' category.
I'd LOVE for you to meet my sensei. He's a "MMA doesnt work" kind of guy. Guillotine = Eyes being ripped out. You go for a triangle on the street? Have fun with that shark attack bite on the side of your leg for the rest of your life. MMA Vs Street Fighter is only relevent as in trained fighter Vs untrained fighter. Someone who fights, even the simple form of karate I also do, gives me the reactions to dodge the reckless haymakers people throw on the street. We do wrist locks and stuff which at least would be able to get their hand off my chest (for some reason people fight with one hand grabbing you and the other with shit punches lmao). Thats really the only difference, fight experience and reactions. Everything is more natural to someone training. If its a real fight, cardio probably wont come in cause you're either knocking someone out or being knocked out. Techniques like submissions and takedowns dont work, because someone will bite the shit out of you if you have them trapped, and I dont mean like the dude bit on TUF, I mean chunks.
And thats me as a white belt (missed grading
) saying that. I know from experience that the high grades wouldnt be phased by someone trying MMA on the streets because the high grades have trained even as simple things as finger breaking, groin grabs, eye rakes and everything that would be "against the rules" in MMA. I mean it's not hard to do it, but if you're going for what you mentioned, triangles and guillotines, you're probably going to be sorry immediatley after it. Best bet is to use your natural fighting experience to put the guy away with punches.