I've been thinking a lot about Dominion as a campaign game, and think that it is entirely doable. But there are various ways to go about it and I'm trying to weigh the pros and cons of each. Here are my ideas:
— Winner Swaps An Estate For A Duchy. Each game, they get to keep and add to their duchies. For 2-player games, the players play five games and determine their combined total scores afterwards. For games with more players, five may still work or the players can play until a player has three duchies (then still play one last game). This version seems the least invasive, but also gives the least real reward.
— Winner Swaps A Copper For A Silver. This mode can definitely balance the game in favor of the previous game's victory, but I doubt it will be enough for that player to win the game if they are skilled. For this mode, I think five games total would still be best regardless of player count, with a total victory points for each player determined after the fifth game.
— Winner Keeps A Kingdom Card. This mode gives the option for the winner of a game to keep one single Kingdom card from the previous game in their deck. They can retain this card over the course of the entire campaign. Think of it as a Black Market reward that keeps on giving. Same rules as Copper; five games, winner determined from total victory points after the fifth game.
— Only Replace Empty Piles. This mode is something entirely original, I believe. Instead of replacing all ten Kingdom piles at the end of each game, only empty piles are replaced. That includes basic card stacks. Run out of Provinces? Too bad! Out of gold, the game may go into overtime. No curses, I don't think anyone will mind. In this mode, each game goes faster than the previous as partially depleted piles remain in play for the next game. Empty piles at the end of the game are replaced with new random piles, as are the starting cards. Player decks are removed from the game at the end of a game, though each player still starts with 3 Estates and 7 Coppers, leaving the Supply piles alone. The Trash remains untouched throughout the entire campaign. End-game conditions are the same. Winner is determined after the seventh game rather than the fifth. This mode may also work well in combination with the first idea, of the winner adding replacing an Estate with a Duchy. Perhaps the very first game of the campaign should use Shelters. Each game should have Platinum and Colony, since Provinces will be running low by the end.
Of these ideas, I like the last best, but it violates the rules of the game more. However, I think it provides for a better campaign experience. I'm going to try it tomorrow if I have time. Tell me what you think. The current campaign rules on BGG are not entirely to my liking.