If you're looking for something other than Text.Theater, Subtxt could be worth a look. It's designed for screenwriters, novelists and playwrights, with tools to construct narrative structure and consistency. Subtxt uses AI to identify gaps in a story and to generate material to fill them, with tools like Narrative Agents, Subtxt Muse and Storyteller's Lexicon. Like Text.Theater, the service can help you flesh out your story while keeping your own voice intact.
Another option is StoryBee, an AI-powered story generator that lets you input prompts or themes and customize the story with different genres, styles and visual styles. It's got tools like audio narration with voice cloning, so it's an interactive storytelling tool. StoryBee is good for kids and adults who want to express themselves, and could be a good way to create and share stories with friends.
Although these two services are focused on creative storytelling, not scene simulation, they both have elements of interactive storytelling and AI-assisted narrative help, so they're related to Text.Theater's particular abilities.