If this "spoils of war" has to contain something in the way of buildings and upgrades i would like something like this
This pack should be hard to get, maybe a 5% chance of getting it with a level 10 GB.
The pack could contain upgrades for old buildings that aint upgradable yet.
Make unlimited levels for these buildings maybe.
Terrace Farm
Elephant set
Palace set
A new production building
A new residential building
Each upgrade/level would make the output 3-4% better for these buildings. (3-4% for the base value each level, and not +3-4% on top of the current output
What u get from this pack should be random, and with 13 different upgrades in the pack it wount be to powerful (inno stil have to keep a coin value to other buildings in the game and new buildings)
Maybe an option of getting the building it self if the game cant find the building in your town or storage, so those without a palace could get one as an example.
This alone would make me build the GB.
Edit: Maybe the % could be somewhat higher it would take a long time to get one of those buildings to just yield one more FP, but im sure the dev´s can se the idea in this an adjust the % so it fits in, if they use the idea for this GB or for something else later.