Usually when thinking about alternate histories of the 2280s, I wandwave away the Probe. It’s all too coincidental. It shows up at precisely that particular moment when Kirk and his crew happen to be the only ship capable of going back in time to solve the crisis. It always seemed to me that, alter any of these events, alter the initial set-up in any way, and the Probe is virtually unstoppable, and Earth dies.
Then, inspiration struck.
I’m not 100 percent clear on what the Probe was trying to do. The movie doesn’t make it clear, and the Federation President talking about “vaporizing our oceans” doesn’t make a whole lot of sense. What if the Probe took a look at Earth, decided it wasn’t wet enough, and the Probe wasn’t “vaporizing” the oceans so much as putting more water vapor into the atmosphere to make the planet more tropical. (How this is supposed to jump-start the evolutionary process I haven’t figured out, but we’ll set that question aside for a time.) The polar ice caps would melt, the sea levels would rise. The Probe, then, was firing up the Greenhouse Effect. Humanity would survive, but life would probably be very harsh. And getting off the planet isn’t an option.
A story idea is germinating. The Federation’s efforts to keep humanity alive on Earth until the Probe either is destroyed or departs are starting to take shape in the back of my mind. Hum. I’ll post more on this as ideas strike.
As for the galactic stage, I’ve always taken the virtual destruction of Earth in the mid-2280s by the Probe as Federation Season; the Romulans and Klingons would probably make an effort to turn the situation to their own advantages, as the Federation’s attentions would probably be turned toward trying to dislodge the Probe from Earth orbit. I don’t see a war, but I could see the Klingons and the Romulans each putting ships in orbit of planets along their respective Neutral Zones that they wanted and daring the Federation to take them back, knowing full well that the Federation has other concerns at that moment.
I think Starfleet Headquarters would move to Mars, taking over the Utopia Planitia complex and expanding.
The Federation government complex in Paris would be inaccessible, and I’m not sure where it would move to. Some long-standing Federation member worlds might decide to move out on their own.
It’s a big change. There’s a lot that can happen.