You can edit save files in a text editor https://itch.io/post/729513 , so you could do something like this:
1. Create a new save file right after starting the game
2. Copy idols from other save file (and make sure that everyone has a unique "id"), change their looks, names, other parameters if you want
When editing "textureAssets", you'll need to add id of your mod, like this "asset_id": "2 0 2 TestMod"
3. People then can use this save file to start the game with a premade group