Here are my ideas on the possibilities:
1. This would end up like the Fox situation, but worse. Every character they touch will be tarnished forever; Marvel won’t want to touch any of them, if they ever could get them back. Where would that leave them? Dumb and dumber (Arad and Pascal- I can't decide which one is which in this situation

) are going to have to do a lot of work justifying pressing on with this as of now to the higher-ups.
2. Sony rips Spider-Man from the MCU, already garnering massive amounts of contempt from the general public, and then uses him as the building block for… what? A universe filled with characters they themselves already failed to adapt? Or the ones that will invariably lead to an influx of MCU/Raimi comparisons? If they can’t build a universe without Spider-Man (granted he is integral to all this), I seriously doubt they can do it with him. It’s similar to your point on a Doctor Doom solo movie: that we’ve only seen a bad Doctor Doom not because he’s a bad character, but because he’s been in bad FF movies. Putting a good Spider-Man in a poorly-designed universe won’t make that universe magically good. Oh yeah, and Sony definitely never has, nor will be, good at taking their time. Gotta get that “quick” Avengers money, right?
3. I think that this has a decent chance of happening- maybe even more than you. As inept as they are, to their credit, Sony seems much less stubborn than Fox, and more willing to form a partnership.
Whatever their announcement, I hope they make it soon, rather than just sitting on it. Although they may end up doing exactly that to put Marvel in a position where they want them. We don’t exactly have a precedent for how Sony behaves strategically (just typing that made me laugh audibly!

), since all this happened because of the leaks, right?
Venom is their crown jewel (crown turd?); if this doesn’t take off, I don’t see anything happening. But trying to make sense of these companies is like trying to draw a square circle. Anything can happen. Haven’t you seen the swarms of people clamoring for a Jackpot movie?