Quote Originally Posted by Hai-Etlik View Post
The energy requirements for altering a planet's rotation like that are up in "if you can do it, you don't need to" territory.
Venus rotates extremely slowly. Stopping it and starting the new rotation on a new axis would be less work than the inescapable need to spin it up to something much closer to an Earthlike rotational rate or Earth-based climate models won't even apply in the first place, as day/night would easily dominate over seasons.