Well, now that the Winter Village set pieces have been proliferating, some people may have enough to be worth a good plunder. And taking a closer look at the bonuses from the set pieces, here's what we plunders should look for:
#1 Moose Meadow. This is the best plunder target from the winter set. It's very similar to the Spring set's Zen Zone, but requires 1 extra piece for the full bonus. At 3 connected set pieces, it will produce the FP. With 4, it produces the FP and the 5 goods.
#2 Toymaker's Booth. A little different from the Moose, the Toymaker gives 5 goods at 3 pieces, and FP at 4. A fully boosted Toymaker should give the same take as the Moose. (Well, I didn't check the coins or supplies, but who cares? That's not why we're hitting these things, right?)
#3 Sugar Baker's Booth. The sugar here is the FP that can be plundered when it's fully boosted with 4 other pieces.
Otherwise it's like the Toymaker, but gives medals instead of goods with 3 pieces. Not bad for the FP, but prioritize the other two for a sweeter take.
The Indian Palace, however, still reigns supreme as far as plunder targets go.
The other 6 pieces can't be plundered. The Halmbock and Smorgasbord Feast offer small combat bonuses, +2% for attack and +3% for defense with 3 other pieces. The bonuses don't increase with age, you don't need to waste 1ups or Renos on them, since the only thing that increases with age is Happiness, and you've probably got a Traz for that.
To get two other pieces for the maximum bonus, Madame Fortuna's Tent and the Straw Star Tent should work well, and both can be acquired simply by completing all the quests. None of those 4 pieces require a road either, the combat bonus pieces only take up 2 squares, while the two guaranteed pieces are only 1x1. So if you get multiple copies of these pieces, they can be sqeezed into unused spaces at the edges of the city or between buildings or something for a bit of an added punch. Watchfires and Ritual Flames are better for defense of course, but the little attack boosts could be handy. The other two pieces are just tiny coin and supply boosts.