I realize you know about the ground work:)
Your pony would be an ineresting challenge. Personally I think you could ride her for short periods and it wouldn't hurt. But then, like you say it wouldn't make her safe for just anyone especially kids. That's too bad too, she's so cute.
You know I have seen so many large large horses that are really more kid broke then kid broke ponies. Poor ponies. They are in a bad postion. Adults don't like getting on them for fear of hurting them, but very few kids can ride one properly for training. We got very very lucky with the pony we got for Jenny. He'd been rode by a girl that was truly and naturally a very good rider/trainer even as a kid. She had the advantage of having a mother who rode alot, and worked with her, didn't just turn her loose on the pony to do whatever. I think he was one of the hardest ones we ever had to part with. Too bad kids have to out grow them so fast. But it seemed a waste for us to hang on to the little guy when there were so many kids out there who could beneift from a pony like him. We kept up with him, and he went thru several more families of kids before we lost track.
Becky