lead rideable horses and llamas

If someone is riding a horse or llama, another person can't lead it. It would be great in multiplayer games if you could lead a horse or llama while someone else is on it. Maybe not horses, but definitely llamas. I mean, they're useful for practically nothing! You can sit on one, and lead it, but it usually just goes where it wants to. We should do this so that they're more useful.  (P.S. I like the fact you can't actually ride llamas like horses, so please keep that!)