I'm going to be honest, I think creating a tulpa is a terrible idea. It won't start badly, but I can't see you being too mentally healthy 10 years down the road. Considering how hard (supposedly) it is to rid yourself of a tulpa, you're stuck with them forever. Making them a pony is a good way to be doubly screwed, as I'm sure most people will tire of MLP after it dies, or as you get older. Also, while you'll likely remain friends with your tulpa for a very long time, the near constant companionship may cause you to tire of them, and you don't want to fall out with a tulpa. I know there are benefits, but I can't help but feel that the eventual consequences outweigh them. Anyway, just my thoughts on the matter.