I would like the one you can ride in Sholazar Basin from the flight points, you know, the planes. I think they're pretty awesome. Add them to the engineering profession as a new higher level recipe. I'm sure I'm not the only one who'd love one of these as a mount.
I'd also quite like to see some boat mounts, that maybe you could even fish from. Or a submarine mount. There's not many water mounts for obvious reasons, but a few more selections could be fun.
What would you like to see in the next expansion?