AOM: Diplomatic Immunity

I'm adding a house rule to Army of Magic to try out.  (Skip to the bottom of the rules post if my reasoning about why/why not is painfully boring.)  The concept has met with criticism from friends based on it being too restrictive, but more on that and why I hope they'll experiment with this in a moment.

The Initial Thought

In my last post I mentioned that I like the Dethrone mechanic introduced in the Conspiracy multiplayer format.  To sum it up quickly, a creature with Dethrone gets a +1/+1 counter whenever it attacks the player with the most life or tied for the most life.  My initial suggestion was that we similarly restrict creature attacks to the player(s) "most ahead".  Probably a bad idea, as it was met with some very sound reasons not to even attempt this.

Cons

First and foremost in aversion to this approach is the observation that in Magic, life is a resource, one of several resources.  Just because a player has the most life does not mean they are "winning" or "ahead" in the game.  Conversely, a player with very low life (even negative life) may be a significant threat.  Second is the argument that multiplayer Magic is a free-for-all simulated brawl to the death, it can be brutal by nature, and only the strongest will survive.  By this logic, if a person builds a consistent deck and uses good battle strategy, they deserve to win games and shouldn't "have their hands tied" by being restricted on whom they may or may not attack.

Pros

AOM is a multiplayer format by design, inspired by EDH/Commander, which has a philosophy "designed to promote social games of magic."  The EDH core philosophy goes on to say "House rules or 'fair play' exceptions are always encouraged if they result in more fun for the local community."  I've been made acutely aware in discussing rule changes that "fun" is subjective, but let's establish some assumptions based on a correlation between "social" and "fun":

• More Casual == More Fun.  In AOM, like in EDH, as players and friends we want to talk.  We want to relax and joke and discuss more than just the details of the game.  Casual play is naturally less competitive than dueling, and we can't take the game too seriously and still enjoy ourselves.  This doesn't require ignoring the rules, but it may mean occasionally sacrificing the most effective battle strategy for allowing another player to keep enjoying the game experience.
• Longer Games == More Fun.  It's not a tournament, and we're not facing off with another player with a goal of winning as quickly as possible and moving on to the next match.  A 1-on-1 duel is like a cage match; a multiplayer game is more like a complex war between several factions.
• Staying In the Game == More Fun.  Good battle strategy often calls for eliminating one threat quickly so one can focus on other threats.  I'm suggesting that AOM isn't designed for perfect battle strategy.  Remember that it simulates a war, not a battle, and wars suffer from the complications of politics, diplomacy, and orders that may be hard to swallow (like "Hold your position and do not engage the enemy.")  If the players are sitting at the table to play the game, it won't be fun for any of them to be quickly eliminated.

As an inverse illustration of the last point above, one of my friends doesn't highly enjoy Magic; he plays out of courtesy to his nerdy friends like me.  I can't speak for his reasons, but I can imagine he doesn't appreciate the level of hostility inherent in the game combined with the element of luck--if you have terrible card draw, you'll probably lose regardless of the strength of the deck you took time to construct.  Given this particular friend's dislike for the game as a whole, he specifically contradicted the assumption that Staying In the Game == More Fun.  From his perspective, the game isn't incredibly enjoyable in the first place, so if I'm not going to win, please kill me quickly and put me out of my misery.

The above perspective and the assumptions before it are a few reasons I invented AOM.  I believe that the universal restrictions to deck building and the Diplomatic Immunity house rule I'm adding will make for longer, more casual, more participatory, more balanced, more fun games that players will want to stay in to play.

So what is the benefit of restricting attacks based on some measure of power/threat in game?  Multiplayer free-for-all games present a challenge to players: who should I attack?  How many blockers should I keep?  It's easy to form both grudges and temporary alliances based on the politics of the game, and if you happen to be targeted or even bullied by multiple opponents it's sometimes difficult not to take it personally when you're quickly dispatched from an otherwise lengthy game.  See above, Staying In the Game == More Fun.  Another difficulty may lie in not wanting to target a specific player to avoid hurt feelings between friends.  Personally, I've found these problems to be most severe in 3-player games.

Some formats already exist that help to address these issues.  Star format pits each active player against a 2-opponent team, but it typically requires 5 players and in its purest form involves 5 mono-colored decks.  Emperor and Two-Headed Giant both establish teams so everyone knows who their friends and enemies are, but again they restrict number of players and have other limitations that complicate the rules.

Enter Diplomatic Immunity.  As the tides of war ebb and flow, power shifts from one player faction to another, and orders descend from above to avoid valuable targets: potential allies and lesser threats who can be dealt with another day.  The key benefit is that nobody feels threatened/targeted for long, unless they make themselves a bigger threat.  Everyone stays in the game longer as equal powers strain to tip the scales in their favor.

The Actual Rule Already...

All opponents to the active player can attain a state of Diplomatic Immunity on each turn by meeting 3 conditions:

• No planeswalker on the battlefield AND
• Less non-land permanents on the battlefield than another opponent AND
• Less life than another opponent

The active player cannot attack or target an opponent with Diplomatic Immunity.  The active player may target the permanents of an opponent with Diplomatic Immunity, and effects that apply to each or all opponents or players still apply.  In essence, a player with Diplomatic Immunity has hexproof until end of turn and cannot be attacked in combat.  All effects that add or remove non-land permanents including permanents with Flash, and all effects that alter life totals, can immediately change the status of Diplomatic Immunity.  Examples:

• If an opponent who has Immunity casts a creature card with Flash and subsequently ties for most non-land permanents, he or she loses Immunity and may be attacked and targeted.
• If each opponent takes 2 damage but one prevents the damage, and an opponent without Immunity then meets all three criteria (no planeswalker, less permanents, less life), he or she gains Immunity.
• If an opponent gains Immunity during a combat phase but was already under attack, the attack proceeds and combat damage will be dealt.
• If an opponent gains Immunity during a turn but a spell targeting that opponent is on the stack, the spell resolves but has an illegal target so the effect will not take place.

I welcome comments!  Let me know if you think this will or won't work, what benefits or challenges you suspect it may cause, and of course your actual experience if you try it out!