Jubal - Each of my decks is a different era in history - ancient, medieval etc - so that was the justification for splitting them up. I wondered if this would result in a sudden change in gameplay each time a new era was reached, but in fact the evolution of gameplay remained fluid. Catan is an interesting example, I think you're right the only purpose cards serve, besides practicality, is the ease with which they can be fanned out for a randomised theft. Another plus!
Clockwork - thanks for sharing the video, I really like the idea of new cards evolving out of gameplay. Great way to get the audience involved in the lore. I don't know L5R so I have to say I was picturing MTG for most of it, but I think I got the idea. Bringing out personality through mechanics as well as flavour text is really interesting. I've also been wondering about creating a Legacy game, in which each play through builds on the one before it mechanically and narratively (if that's a word), and using actual playtesting events to influence the plot. For example, if playtesters favoured a certain faction at one point in the design process, there could be a scenario in which that faction is dominant.