As much as a penny farthing* would rock, I think any mount would need to be able to handle rough terrain and step rocky slopes. Wheels won't cut it, IMO.
You
might get away with tank treads...
I'd suggest looking at the gnome racial mount and working out how to expand on that idea. Pick another animal, make a robotic version, and bam - new engineering mount.
Just remember there's a 20% chance of the mount blowing up 30 seconds after you summon it.
* That's the vintage bicycle with the huge front wheel and tiny rear wheel.