I think this would be a great addition to the Clash of Clans Experience i envision it as a Tab Similar to Village Edit Mode that would allow you to deploy Infinite troops on your own base to test Concepts and Defenses. There would be no loot gained or lost and you couldSwitch to edit mode from it to Make changes According to the Testing. This is My Idea of a Great Addition To Clash of Clans Please Give Your Opinion and if you think you could improve on this Idea and if so Please Post How.
1: search function, many people made made threads about this
2: I think that any type of 'sandbox mode' (your base or clanmate's base) is ruled out, mainly because people can abuse it by making their base into their enemy's and then flinging the best troop comp then destroying the enemy's base