Regarding Gift Cards still allowing for trolling: I don't think it's possible to completely eliminate the problem. For instance, instead of boxing in one territory a troll could box in a small group of them, conquering one just before any anti-trolling mechanism activates. Even if that fixes the problem in theory (by limiting the troll from an indefinite amount of time to a limited amount of time), if a troll can still keep going for hours, the problem isn't solved in practice
Good point about lots of Diplomacy Cards. There might be an easy solution for that though: simply not counting any turns where at least one Diplomacy Card is active.
Truthless Hero also has a good point, which I'm not certain how to address...
Any argument only valid for the map Pirate vs. Ninja is (as far as I care) moot.
I do have to say I like Hennns counter-suggestion. It might need to be tweaked / detailed a bit though:
- If two non-surrendered players are on the same team, I think the mechanism should still trigger. So the rule should become something like "if all players except (some of) the players on Team X have surrendered and all surrenders from players not on Team X have been accepted by everybody not on Team X, all surrenders (including any surrenders of players on Team X) can be accepted". (I removed the "... and the game ended" clause, see next bullet.)
Yes, this gets slightly messy to explain in one sentence. Maybe a step-by-step explanation would be more clear. Explaining corner cases with examples is probably also easier.
- Any AIs should probably be left out of consideration. (This is true even in games where they are not set to surrender themselves; once all-but-one human players consider a game pointless, they should be allowed to leave. They still turn into AIs, at which point the sole remaining human can try to finish the game.)
- I'm unsure whether this should happen immediately (automatically), or whether it should only enable a button, or popup, "force surrender" (or prevent unwanted triggering through some other mechanism).
On the one hand, cluttering the interface is bad, on the other hand, triggering when not intended is bad... I've been in a few games where one player offered to surrender but (by mutual agreement in chat) it was decided to play for a few more turns (or, to the end) anyway.
Note that automatically triggering would mean the option "surrenders have to be accepted" will lose all meaning on two players games (I'm not in favour or against that, just an observation).