There are several frames associated with the compass that would all need to move as well. All of this is somewhat possible, depending on the level of "hack" that the developer goes to.
There are future plans to add this kind of thing to Full Immersion but no idea when I'll get around to it. It could be a month or more.
this needs to be in already, looking too far up or down at a monitor is just bad design and EVERYONE knows that. Just because it's been that way in every ES game does not mean everyone likes it. As a matter of fact, most MMOs these days have a fully adjustable GUI... soooo figure it out DEVs.