The ability to move a group of posts from one category to another seems like a natural function that has been overlooked.
I use WordPress as the basis for several storefront sites. I populate these sites using the FeedWordPress plugin or WP-o-Matic plugin. If I want to move all of the products from one category to another, the fastest way is to unsubscribe the feed, delete all the posts, and set it all up again to repopulate them into the one I want. That is a very unwieldy process, and I am not sure what SEO benefits are lost this way.
As a related issue, I would like the ability to increase the number of posts in the list on admin screens. That would also speed up the management process.