So, taking aside all aesthetic and marketing concerns, because I'm only interested in talking about game mechanics in this thread:
What are the core gameplay elements that make Legend of the Five Rings the game it is, without which, it would no longer be Legend of the Five Rings? Why?
For me, a big one is the balance between Honor and Military.
While I have some issues with the death spiral of province loss, some of the most tense games I've played involve racing to break 40 honor while desperately defending your dwindling holdings. In principle, I love the ability to sacrifice honor for the sake of expediency by buying corrupted units and holdings, or hiring a Ninja to assassinate an opposing personality, but suffering for that choice by losing access to certain honorable personalities, or other consequences. I have some problems with dishonor effects, also, because they sometimes seemed arbitrary; but effects that forced you to make a choice between suffering a negative card effect honorably or taking an honor hit instead were some of my favorites, even though they often seemed difficult to balance.
Without Honor and its impacts (positive and negative) on Military and other game effects, a huge part of L5R would be missing for me. Enlightenment wins I can take or leave -- I'm just as happy leaving the 5 Rings as abstract, symbolic ideas and not manifesting them in game play. They're just a legend after all. But if the new game is indeed an overhaul of the old, it must have Honor and Military victories (I'm okay with Dishonor not being a win condition so much as a control strategy to make your opponent's life more difficult and achieve a win through other means.)
Provinces, Battles and Honor through victory. The four provinces and the battle phase are a core mechanic for me, and a lot of strategy comes from how much of your force you commit where. All out attack on one province? Split your forces and try for two provinces, knowing that you're probably sacrificing one army for an easy victory at the other province, or perhaps as a feint to draw out a weaker opponent so you can crush him with the combined might of both armies? This connects to military and honor victories above, in the sense that you could get a quick jump on military might by sacrificing some honor, but redeem it through victory on the field of battle. Just as true, you could try for "clean" victories in battle, with honorable cards, and use the honor you gain to rocket to victory.
Dueling: In addition to being an elegant little mechanic, dueling introduced an important secondary consideration when adding Fate Cards to your deck. Just how important is that focus value? It wasn't always consistent -- it seemed that sometimes good cards had high focus values, so you had to choose between playing to from hand or losing a valuable card for a dule; while other times it seemed as if powerful cards had low focus so the decision was not in whether to play the card, but whether to include it in your deck at all.
In fact, I would go so far as to suggest that some sort of "built in" dueling mechanic might benefit the game. Some way to allow personalities to issue duels without card effects. Perhaps a dueling phase in battle, where each player (or perhaps only the defender?) can initiate one duel, but the result is only to send the loser home bowed. Whatever it may be, I think it would be neat to make dueling something that every deck must at least consider, rather than simply ignoring in the hope of not meeting a dueling deck, or being prepared to write off duel losses. Of course, the flip side of this would be that it would be very difficult to build a dominant dueling deck. I'm not so sure that's a bad thing, though.
Followers and Personality Protection: I really liked that Personalities were often treated more like generals than like individual heroes charging off to burn down enemy castles, and the protection followers granted to personalities was a big part of that. I wouldn't mind seeing more encouragement for non-military decks to play followers as well, and perhaps more followers will have effects other than force bonuses.
What are some of your requirements, without which a new version of L5R can no longer be called L5R, and becomes a different game entirely?