Depth and Dynamic Objects

I am having some problems with my MMORPG I am creating in Actionscript 3.0, not really errors, but more how to do something, in theory. I have 2 problems. First, my game is at a 45 degree angle, so it requires some depth handling. I am not sure how to go about this. I was thinking that each object’s depth should be it’s y position if it’s origin was at it’s feet. But that idea didn’t go well. What is the average way to do this? Finally, I am trying to make dynamic objects, so that all I would do is copy and paste an object, or create a new class of it and it would work. What I mean is, the character checks a collision for each object, but if I copy the object with the same name, it doesn’t work. In AS3 you can’t attach scripts to objects anymore, so I am running into a lot of problems with that. How would I go about fixing this? Please ask me if you need me to explain something in more depth or better. You can see what I mean about my depth problem at www.emberstudios.net/main.html. Thank you in advance.