After playing around with it, I realized adding this to new scenes would be REALLY easy. I like that. However, I have a few suggestions. Feel free to ignore them if they aren't what you want your script to be like.
First, I want to be able to change the cursor graphic or the icon graphic when one of the icons is moused over. Not a real big feature, but it'd be nice. Second, I'd like the ability to define an icon back (like blizzABS hotkeys), or to have a picture drawn below the icons. Third, I'd like to be able to disable menu items, like in the default menu. The icon would be grayed out and unusable. When you click it, you'd get the error buzzer noise.
If you don't want to make those additions, I'll probably try to make an enhancement add-on for your mouse map menu. I love what you've been doing with blizz's mouse system, it's very useful.
P.S. I know it's kind of a given, but you might want to mention in your post that this requires blizz's mouse script.