I like the idea of warping but that has big problems with powerful mobs that need multiple alliances as backup.

My suggestion is about the same people outside the combat should still be able to see the battle. They won't take damage or be effected by damage unless they join in and receive the icon listed below. The people in battle will switch to a ballista type environment other players and monsters disappear to them.

After claiming players in the alliance get a a special claim icon like those in events so players can't heal from the outside etc without the limit. Similar to garrisons. This is where things change though.

If a player is in the same linkshell of any member in the alliance they can heal or support there friends by accepting the icon becoming a member of the alternate reality.

To make it as simple as possible.

1. (Outside MPK aggros damage and interference)
After claim members of alliance enter alternate reality, that hides outside players and mobs from them, like Ballista events. Players that are in the alternate reality don't see mobs or other players outside the reality.

2. (Allow friends join in and help at any time)
Base NM's icon on the claimer linkshell anyone with friends in the claimers linkshell can support and enter the alternate reality. When a LS member enters an area they are given the option to join the alternate reality. If they are already in that area targeting the NM or attempting to cast a support spell will issue the option to join the alternate reality. You don't need to be in the claimers alliance just the linkshell, however this only allows to support or join in but you can't attack the NM in any way unless you become party of the fighting parties.

3. (Protection from backlash MPK)
After NM or players are defeated they will remain in the alternate reality for 5 minutes. this allows players to receive all loot and escape the area etc. During this time they will gain the ability to see outside mobs until the 5 minute timer is up or given the option to home point. (Just in case someone trained aggro enemies on top of the claimers allience or other ls members.)

4. (Reward on lookers)
Last allow everyone in the area outside the alternate reality opportunity to receive a treasure like the ram event buy clicking once on the NM. Maybe a 1 in 999 chance to get something good. This makes it so people who wait for the NM to die have something to look forward to. Most of the other stuff will be junk.

Ok, I've discussed this with my linkshell and alot of friends.
This is an easy solution.

Ala every other Final Fantasy game, with random battles; when you're walking across the battlefied and get warped.

As soon as the NM gets claimed, the person who claimed it, and their party will get warped to a battlefield where nobody else is.
MPK is absolutly impossibe in this case, since their will only be one party/alliance there vs. the monster in question.

If the said party happens to lose the battle, the NM will pop again for the other people waiting who tried to get the claim originally. But the waiting parties will have no idea if the NM is defeated or not, so that would add a bit of strategy.
Anyways, in short, this would eliminate all forms of MPK, while still keeping the world of Final Fantasy alive and well. It's a system used for 10 Final Fantasy's prior so why not FFXI?
Thanks

Sounds nice at first, but then some people will still MPK you if you got the claim first out of spite, regardless whether the mob despawn or not.

I think if they really wanted to stop MPKing. After a NM mob is unclaimed because its opponent is defeated have it despawn. It sucks that no one would get it, but it wouldn't benefit ANYONE if you MPK someone. Either have it despawn or go into a "call for help mode"