I've done exactly this, with a plate that was superglued on to a Cube I bought. What makes it kind of ridiculous is that 1) the shell detaches easily, leaving the expensive core free to be removed, and 2) there's a Kensington slot on the core's handle anyway, which would secure the whole lot!
Anyway, it's easy enough to remove without leaving a trace. I took a long, thin kitchen knife and sawed away at the join between the plate and the acrylic shell. The knife won't scratch the shell, as you're sawing parallel to it. Once the edge of the plate had been lifted slightly, I used a cleaver to get in there and apply pressure. It then let go almost immediately.
Some hard superglue residue was left on the shell. I used a paint scraper (a Stanley knife blade perpendicular to a handle) to carefully remove most of this. Again, this shouldn't dig in to the acrylic, it'll just catch on the glue. To fully remove traces of the glue, I used Meguiar's Plast-Rx plastic polish. It's designed for headlights, helmet visors and so on. With a microfibre pad and a bit of elbow grease it came up virtually as good as new.
The Meguiar's is great for cleaning up scratches on a Cube generally. It'd probably remove any depth of scratch, but obviously very deep ones will require a lot of polishing, and you'd start buffing dips into the surface. Good luck!