I'll admit that I have very little knowledge of the subject, but as it looks like it could be a fun and interesting subject to write, I'm seeking a partner to play a trainer to a new pony. The pony-girl can be a consenting woman who's looking for something exciting and adventurous to try for some reason, or a non-con situation where a woman finds herself being pressed into the role of a pony-girl and everything that goes with it.
I have a couple of vague ideas, but I'm very open to any ideas that a potential partner wishes to offer. I'll be playing the pony, but the sex of the trainer (or the sex of the player) is variable.
idea 1: A young woman wants to indulge her boyfriend's desire to see her as a pet. Of the options offered to her, she selected a pony simply because it wasn't a household pet and goes to a stable that trains pony-girls for a weekend. When she discovers that she likes the feelings that being in harness provokes, she turns the weekend into a several week training session.
Idea 2: The wife of a wealthy man has become inconvenient and her threats to divorce him if he doesn't give her what she sees as hers. If there's a divorce, she walks away with half of what he owns, so he employs the services of a lawyer to get her declaired incompetent. With that done, in a stroke of genius (in his own mind), he sends her to a farm to make her a biddable, obedient pony-girl... however long it takes.
As I mentioned, I'm very open to other options and ideas as well as a variety of kinks and fetishes that a partner may want to include. This will probably go into the extreme category and I'm not opposed to breeding and pregnancy as eventual elements, for example.
If interested in talking about it and developing a story, please PM me.