Revvy
If the PvE env or the opponents get you more than 20 times before you reach your goal;
You are losing the possibility to respawn on this outpost zone (tactically you may respawn on another outpost zone).
So the outpost can be taken over.
And it will push people to be rewarded in the survival, favor the escape route to counter attack somewhere else.
Instead of spawning, heal and comeback infinitely.
Hmm. I think the outpost owners would already be at a tactical advantage from simply having the outpost, and the accompanying NPCs.. The attackers still have to spend time to destroy the outpost building -- for a well upgraded outpost this may already take longer than traveling an army back to the outpost. Also throw in healer NPCs (spawn yourself a healer squad instead of respawning), and you've got yourself a pretty nice fortress. Giving the defenders a 'multiple rounds' advantage seems a bit too much 'easy mode' and may tip the balance too much.
Let's say you have a pretty good guild with a nice outpost, and some allies. You've got another guild attacking your outpost with their allies[*]. Your guild can quickly port into the outpost the first round to do the initial defense, together with NPCs -- at this point you have a guild with their allies attacking vs. a guild with NPCs, which can be relatively fair. Your allies are traveling in. Perhaps you fail to defend your outpost, and you all die. Maybe you have your allies tactically wait for your team to join up, or you have them advance. Either way, let's say the opposing guild destroys the outpost building. At this point they can build and have a weak non-functional outpost building -- and now they become the defenders. However, as long as the buildings are not constructed and not upgraded, they cannot get the NPCs yet. You are at this point still completely capable of regaining your outpost, by attacking it, and neither guilds have an advantage now.
Though, if one of your allies happens to have an outpost nearby, it can serve as a regrouping base... Perhaps they could even dispatch their NPC guards.
[*] An alliance system between guilds. Works like making facebook friends. In GvG anyone should be able to heal anyone directly, and allies can still be attacked directly (betrayal!), but AoE healing spells should only affect guild members and allies, offensive AoE should only affect non-allies.
At some point the whole process becomes a battle of resources. Either guilds fight each other to attempt gaining whatever they can gain from outposts, but they end up draining each other's resources.. and in the end the Kitins win... or... There should not be any artificial boundaries or disadvantages to launching an attack, to ensure that a stalemate doesn't develop. :)
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Kaetemi