Back in 3rd edition when the vehicle design rules came out, I had made a couple of fliers for my dark eldar. I got to use them quite a bit, but they were only able to be used when both players agreed to their use. For me, that kind of defeats the purpose of the standard game, which means they did not get used that often. Getting to use them in every day games would add a new dimension to the game. This summer we just may get to see a rule set that could find it's way into next edition.
Here are some pics of some of what we might be expecting to see this summer. These were taken off a thread on Heresy Online. These are not exactly what we are going to see, just examples.