I have this issue because I want to wrap XenForo inside a container element. I don't want XenForo to have any control of the body element. Ideally I don't want any xF CSS to touch anything outside the container the forum is in.
At the moment XenForo's CSS reset and lack of classes on elements such as headers causes me styling troubles in many ways. My design philosophy is quite different from xF way of doing things, as I base the site design on normalize instead of resetting everything and I give CSS classes for almost everything so generic styles don't leak all over the place. To really properly fix reset issues I'd have to remove all base resets and instead give those rules to the CSS classes that actually need a reset. However as a temporary solution I'd simply want to do a quick retarget so that I don't need to spend all of my weekend just fixing CSS. Which leads to the question I have.
If you're wondering why I want to have control of body element you can take a look at the currently running MyBB installation. It's not your standard looking software. I got started with xF a couple of hours ago so I don't have anything live yet.