I say horses are a tired means of travel and we badly need a new mount type in TES, especially after the dragon mount disappointment so I say saber cat mounts would be perfect...this is how I think it should be done:
We get a quest to see a special animal tamer or something to that effect, a recluse camped out somewhere in skyrim who's currently taming saber cats. We pay him for training to tame our own wild cat (it can work as a power) or buy a tamed cat from him. Once we "own" a saber cat then it should work the same as dogs and horses combined whereas it will follow us everywhere and fight with us but at any time outdoors we can mount it and ride. There could be 2 types of mounted combat, equipping weapons/spells as we do on horses or just hitting the attack button with weapons sheathed to make the saber cat lunge/claw foes.
If for some reason we don't want the cat following us anymore then we can do the same as dogs and tell it go home, if we don't have a home then it will return to the animal tamer and wait for us there.
What do you think? Personally I would gladly shell out 400 MS points ($5) for this.