I thought the whole idea that an oversized moon can greatly reduce the atmosphere of a planet (thus the differences between Earth and Venus) was discounted in the 70s.
How about self replicating nanobots and a tractor beam? Just turn the molecules into what you want them to be and tow the planet to a better orbit. Easy 
Hey, we’re all overlooking the greater issue, here… what if the Venusians don’t want us to terraform their planet?
It was. Virtually no one would even remember that hypothesis if it hadn’t been incorporated in a Larry Niven story.
Just spin it like a CD and it won’t fold. To move the planet you can use a large astroid and alter it’s course so it orbits venus and jupiter, eash pass will pull venus further out, but earth’s orbit will be difficult to cross due to the gravity of earth and chance of collision, then mars
Well, so we’ve all come to the conclusion that we need to find some way to make Venus more geologically active. Any ideas how to do that? Assuming we can solve the atmosphere problem, how do we make volcanoes? Would just sinking shafts into the core do it, or would it take more work. Also, would there be some way to create plates, or seperate the crust somehow?
We’re talking about a screen that’s 1 mm thick (or less) and 12,000 Km across. We’ve never made anything near that size and even if it were spinning, we don’t know how it would behave. Most likely, it’s impossible to make something like that. Besides, it wouldn’t go with my joke.
[white imperialist voice]
But they’re not doing anything with it. It’s just sitting there. They’re too primitive to understand. Give them some iron kettles and beads, maybe a few CD players and Coca-Cola t-shirts, they’ll come around.
Let their headman have the liquor license, that’ll do it.
[/white imperialist voice]
Worse yet, what do we do when the Venusians decide to Veniform Earth?
And before you know it, there’ll be Venusian casinos everywhere…
Aren’t we doing a pretty good job of that ourselves?