When I first started doing layout for RPGs, I was given marked up text and I tended to use that early on. The copy would come from the editor or author and be full of what looked like HTML in brackets or angle-brackets: [em]this would be set in italics[/em], <dice>8</dice> would mean to put in an 8-sided die graphic, while [ih]this could be an inline header (and it took me forever to find out what “ih” meant). The work would consist of taking this plain, unstylized text, and doing several grep searches inside InDesign to replace the markup copy with stylized copy.
For projects like The Fate Codex, I had this pretty much down pat. It worked for that because that project was a series of documents, all using the same paragraph and character styles.