I'd also keep Abrams to direct, but throw out Orci and Kurtzman. They should have at least put someone smart next to them, an experienced Trek writer for example. Someone to tell them "you're lazy, we'll need to come up with a proper solution to this problem".
As for story... I'd keep the actors. Movie starts with your typical action scene, explosions and what not. Set pieces blow up, the whole nine yards. Then after the battle ends (maybe with the death of all heroes) the holodeck gets deactivated. ST11 and 12 have happened... on the holodeck. Some sort of holonovel/Starfleet training exercise. The characters, as we met them, sort of are real, just the names are different. It's a new crew. They are being congratulated for having successfully beta tested a new way of final exams from Starfleet Academy, a 1-2 month holodeck simulation meant to test cadets to their fullest.
They go to their mission of doing cartography or whatever. Cut. We're introduced to the villain of the week (this could happen as the first scene too, or it could be left out until a flashback/flashforward happens). Again, shit blows up, alien planet fights for survival, is being destroyed by someone evil. Only one ship survives, captained by the villain. It's some time in the future. Captain is in fact a scientist who was doing temporal research (yes, I'm recycling a Voyager plot now...) who just wants to restore his planet, and has found out that if "Kirk" hadn't been born, his grand grand grand son wouldn't have destroyed his home world for greed and stuff.
So he decides to go back in time to kill "Kirk". Fighting ensues (that's what people want...) with the "Enterprise" crew being confused what the heck is going on but defending themselves, luckily they start to communicate with "Kirk" giving a rousing speech with lots of wild gesturing, and somehow they figure out a way to end the war, maybe by castrating "Kirk".
Or perhaps it was an idea that "Kirk" had, a movement that "Kirk" started, a philosophy, that ultimately went wrong and led to the destruction of countless worlds. Maybe it was a book that he will write, maybe it is his way of life, have to figure out something plausible that can't be easily undone by a vow (or maybe the villain captain wouldn't accept it). So to stop it, "Kirk" has to die. Maybe the baddies give the Enterprise crew one hour to say goodbye/surrender "Kirk" for execution, and "Kirk" is considering and pondering if what the other side wants isn't sensible. Can he be held responsible for an idea that he sparked? Does it even matter? Doesn't the lives of many outweight one live? The Enterprise crew could come up with a flaw in the enemies shields, making it possible to destroy their vessel. But "Kirk" says no.
Basically it's the classic would you kill Hitler's father story/would Hitler's father kill himself/his child had he known what monster he created. Not exactly original, I admit, but at least there is something to think about.
In terms of structure (and rethinking the mess above) I would have the introduction done in the first 15 minutes, with the revelation it was just a "dream". Then soon thereafter the fighting begins, "Enterprise" is basically lost, all that still works (barely) is the life support. But the bad guys think it's only fair to let the Enterprise crew know why they were attacked, and to give them the chance of survival. After all they only want "Kirk". The pondering part, with different parts of the crew working on different solutions in parallel could set in after maybe one hour, and take maybe 30-45 minutes. It could be done quite tense with ship systems failing and the ultimatum looming over them. And then the conclusion, which the enemy may or may not accept.
That would be the basic 5 minutes of thinking + then some typing and brainstorming to come up with plot. Could probably be fleshed out in the hands of a good writer (which I am most certainly not).
Or maybe just do a NC-17 movie set on Risa.
As for the thing that you'd have to dumb down a movie to get popular/good actors? Not really. Either a big paycheck, or do a project that is challenging, cool and interesting. Brilliant actors are willing to work for next to nothing, if it is NOT a stupid lowest common denominator movie. Things they are really interested in (IMHO those really good actors tend to be rather smart too). Btw., Vin Diesel? His first movie was written, directed, scored and produced by him, it got played at Cannes and impressed Spielberg so much that he wrote Diesel a role in Saving Private Ryan. Sadly Vin Diesel is typecast for a certain kind of action role these days, but hopefully one day he gets the chance to show off what he really can do.