I've had a project going on like this for 20 years myself. Finally gotten enough worked out on how to do it that I think I can make it. It won't be perfectly

I've had a project going on like this for 20 years myself. Finally gotten enough worked out on how to do it that I think I can make it. It won't be perfectly different every time but variations (sometimes small, sometimes large) on 3 main 'stories' that are all potentially happening at the same time, each one from a different perspective. Most of the world is procedurally generated except for a few key things that are either too difficult to work out how to generate or need to be fixed to be able to more easily work out the story there (say towns and specific rooms in buildings).