I've seen it happen believe it or not. There is also the possibility of someone grabbing your balls as well. Guillotine? Sure thing. I've seen guys put a thumb in the eye or the rib and that choke doesn't last long. And hey, I never claimed to be a black belt or anything (I'm a blue belt) but I've been training about 2 days a week for 2 years now and have yet to miss a day. I'm also not arguing that a pro fighter would definitely get beat in a street fight, I'm just saying it's much more possible than people like to think. There's no referee, no rules, no one to pull you off when you aren't protecting yourself.
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.