I think it would be fun to punish a sub by making them sit in a chair in the corner for a “time out”, except there’s a dildo in the middle of the seat that’s way too big for them to take comfortably, and they’re very firmly tied down so that there’s no way for them to escape the feeling of being stretched out and stuffed full. I’d take special care to tie down their hips so that every little movement they make would press the tip of the toy against their cervix with the full weight of their body.
Maybe the amount of time that they have to stay in time-out would vary depending on what they did to earn it, too. Five minutes for something minor, fifteen for something worse, etc. l, and at the end of the time limit I’d ask them to tell me what they did wrong and how they plan to avoid doing it again. If they can’t give me a good enough answer, then the time starts over. I bet that would be a pretty fun punishment. Well… fun for me, at least.