That functionality already exists. Start a new game and make it a new save. It doesn't matter if a lot size you want to build on is already occupied. Just demolish it and build whatever you want. It doesn't matter if you leave your build on that particular lot as it isn't your main save. It doesn't matter if you do decide to demolish it anyway because of you having the non-committal trait. It's not your main save. You can upload anything you build from here onto the gallery and share or show it to other players without it having impacted your main save. And you can download your build from the gallery to your main save if you decide on it any time you like.