Second and third place matter for rating purposes. So people would have to agree on that as well.
It could be:
1) Last player offers to resign.
2) Second player can accept second place --> game ends
I agree all the trailing players need to agree to freeze the rank order in the game by ending, but I think having the second-place player propose joint-resignation would be a superior protocol.
I see the site owners don't regard this proposal seriously enough to comment on the feasibility or desirability.
Plainly you're right. I really wish they would take the proposal seriously. Twice now in as many weeks, I've been in 3-player games in which it was absolutely clear for the last ten rounds at least who would be in first, who would be in second, and who would come in last, but there's no way to end it and go on to the next game without someone taking the punishment for resigning.
Usually this is in a game where the winning player's turns are interminable because s/he found a clever combo the others didn't notice, so it makes having to play it out all the more tedious.
A lot of the discussion on this thread was completely moot vis-a-vis the proposal, since it was about the mechanics of a single player resigning. That's not how this would be implemented: it would need to be one of the trailing players pushing a new button to offer ending the game with the current ranking of players as 1st, 2nd, 3rd, and the other trailing player pushing a new button to accept and cause the joint-resignation. No single player would resign ending the game.
Yes, it would take a little bit of programming, but nothing on the scale of what's already been done. I think it would encourage more multi-player play.