I would highly recommend this reading:
David Chart shared the guidelines he was sending to authors writing for Ars. You should not take that as a limit to what you should be writing or not, more as a guide to understand why Mythic Europe and the range of published books is like that, and what was the intend of the editor.
You will see clearly some limits set in stone.
The more you move away from this status quo, the more likely you might have to adjust other aspects of the paradigm, you might find incoherent situations and you will have to do more finetuning. Not that you should not do it, just that discussion might become more challenging as you move away from the paradigm people are used to work with.