The Instance #179 & #180 talks about new mounts, and by all things holy I think we can go way past riding Hoverboards and Wasps, we can reference the fun ideas in a shared topic on Blog Azeroth, which started it up for me a while back in August 2008.
We might soon see submarines, and all sorts of oceanic mounts. I expect I’ll never see the phoenix or another ultra-low-drop-rate mount, but some of the stuff the Instance crew talk about in #179, and touch on in #180 is interesting.
Just saying its a great thing to add in an expansion, gives breadth of fun to everyone, and has no balance issues to speak of really. And I kind of support a Jetpack for Engineers; more so it can explode or go out of control.