Here's my 2 cents on what you're looking to do. Orthographic views can easily seem like an obvious missing feature in SL, if you're used to using them in 3D modeling programs. However, if you really think about it, it's arguable that they'd be of little or no benefit in SL, since there's no universal grid origin, no common point of reference for multiple cameras to coordinate. They might be helpful; they might not.
That said, technically, you COULD script an object to take control of your camera, if you really want to. For the specific how-to's, I'd suggest you ask for help over in the Scripting Tips forum, as that's where you'll have the best chance of finding an expert on this kind of subject. You could probably create a HUD with some buttons on it, for recording and repeating camera coordinates, relative to your avatar. In theory, as long as you don't move the avatar, it should work.
It's also possible you might be able to use exact positioning instead of just relative positioning, but I don't know for certain. My scripting knowledge is pretty limited.
Really, though, I think this would all be far more trouble then it could possibly be worth. The existing alt-mouse camera controls are very, very good.
I don't know if you fall into this category or not, but a lot of people who ask about additional camera views and such tend to be those who have been using the onscreen camera controls, rather than the alt-mouse controls. If you are in that boat (and by "you" I mean anyone who's reading this is, not just the OP) then you've got every reason to be frustrated with the difficulty you've experienced in operating the camera. If that's the case, let me help you out of that right now.
Those onscreen controls are some of the worst things in the history of bad things. They're horrid. They should never, ever, ever, ever, ever be used, period. They're clunky, imprecise, awkward, slow. Human vocabulary simply cannot express how limiting and just downright silly those controls are. Do yourself a favor and forget they exist.
Instead, use the alt-mouse system. It's far more accurate, infinitely faster, much more controllable, and most importantly, very natural feeling to use. It habitualizes quickly, and from then on, looking around in SL becomes as intuitive as turning your head in RL. You just do it, instantly, without even thinking.
Simply hold down alt, and wherever you click will become the focal point of the camera. Drag the mouse to zoom and rotate. Adding ctrl and shift along with alt will open up further rotation and panning options. Here's a quick diagram of how it works:
This might take a little getting used to if all you've ever used before are the on-screen controls. But after a day or two, tops, it will feel completely natural. You won't even think about it.
So, if you want that instant top-down view, instead of activating a script function, just hold ctrl-shift-click, and push the mouse forward. Want a side view, just hold the same, pull back on the mouse, and then alt-drag to the side, to rotate the view around the object. I think you'll find this to be far quicker and easier than fidgeting with buttons on a HUD or entering text commands or anything like that.
