The key to figuring out why we can’t remove those preinstalled apps yet might be in the quote from Tim Cook to Buzzfeed back in September:

“What might happen, for example, if someone were to click on a Web link after removing Safari? If another browser has been installed, the operating system needs to be written such that it would open in that other browser. If Cupertino didn’t build that particular functionality into iOS from the beginning, it means rewriting quite a bit of code. Since we can’t set a different browser as our default, it seems safe to assume that iOS does not yet offer that functionality.”