To make things easier, couldn't the luggage carts just go around the wings as they do in real life and not go under them? They would surely avoid the cones then.
We are looking into this for handling the front luggage train but, again, it's not really 100% fool proof solution, because on some airplanes and some parkings, there's not enough space for the cart to turn around, without being in a position were its animation wouldn't work anymore.
Guys, sometimes it seems you believe we don't *think* the most obvious solutions: we obviously do, but we have way more things to take into account that what might seems at a first sight, including future expansions you don't know about, and all the interaction between them.
Yes, of course, if the FSX engine was more advanced, we could have smarter vehicles, avoidance (there's a whole lot of programming literature about it, it's a well coded problem), crowd simulation, etc, but we must work with what we have.