(2p games only) When one player has achieved guaranteed victory by having more than half of the available VP, maybe display a message to the losing player and make the resign button more prominent for them?
Obviously there are a lot of kingdoms where it's not as simple as "I have half of the printed VP in the Supply, my victory is guaranteed" but sometimes the game does get to a state like that, the trailing player doesn't know they have no mathematical chance, and the player in the lead needs to take a few turns to empty 3 piles, or hit $8 a couple more times, or whatever. At that point, there is nothing interesting for either player to do, so it'd be in both players' interest to end the game now.
There's this early phase in your Dominion experience where you're kind of taking a Timmy approach to the game, just kind of seeing how good of a deck you can build, and not worrying super hard about whether games are technically winnable. I would hate for this feature to put a damper on early Dominion experiences - it could be frustrating to have the resign button glow right as the final Village that really makes your engine start Provincing each turn gets into your deck, while you are still practicing building your first few engines.
The implementation I would prefer is that the VP total for the player who has the victorious amount of points glows, without any indication of what that means.
In games without the point tracker, the feature seems inappropriate anyway.
Definitely would not want this in games without the point tracker.
For me, when a game gets into this state, there are no more interesting decisions and I'd rather get started on the next game.
There have been discussions about players resigning but you still want the fun of playing out your deck, so the player who resigned gets replaced with an AI; maybe instead of encouraging resignation, we could have sort of the inverse of that: you have a guaranteed victory, so you can leave the game to find a new one, while your opponent has the option of playing to the bitter end against an AI.
Maybe that solution is still too unfriendly, and it's true that this situation isn't
that common (especially with good matchmaking--assuming there are enough players online to find you an even match), but it is really irritating when it does happen.