With the bounding box idea, I was more thinking I could make my own function to get it and then use the "affect all descendants" to get the bounding boxes of all the descendants.
Also, with "physical" markers, it doesn't really seem to work for me because of the loading times since what I'm trying to do with mine is to make it as simple as possible, and then export it here as a file that people can download to make their games on.
I have tested the "physical" markers using small spheres on a terrain generator I tried to make using the diamond-square algorithm, however it took way too long just to get the markers set up to change the elevation of the ground. This could be fixed if I can have multidimensional arrays, and/or a function to create/copy an object in real-time.
I've also pretty much stopped going into Alice too much because of it's limitations and how unstable it can be towards certain aspects of it. I'm starting to switch more to lua, which is an easy language to understand, is based off of C and looks like a pretty good choice to get a step up from Alice (although it does have it's limitations as well).
Here's a site I've found that might help with learning about bounding boxes, and collisions:
http://www.toymaker.info/Games/html/collisions.html
The site does have the information based on a different language, but it does explain it quite well and it also tells how collisions work in other situations as well.