I think a simple user interface showing all available village upgrades would be a handy tool for serious players.
I can spend a lot of time looking over my base to determine what is still left to upgrade before upgrading town hall. If there was a button to push to get a list of all upgrades sorted by cost, this would be a great tool for the user. It could show all buildings, defenses, troops, spells, etc. that can be upgraded and the cost to upgrade.
