Ramidel was the original poster in [url]https://forum.atlas-games.com/t/unstructured-and-rigid-rewrite/10676/1] which discusses this.
I think unstructured could work if you have a Bjornaer with Life-linked spontaneous magic - most of the time you spontaneously cast, when you really need a big spell you can create it with massive fatigue expenditure, and you can use your heartbeast for some things (maybe you took a flying form, or a really stealthy form, or a predatory form). You need to try and get inner heartbeast and a good score in Bjornaer Mystery Cult Lore as soon as possible - once you get it, you can add all the qualities to give you more fatigue levels and some fun tricks, and virtues and powers to add extra capabilities.