Attackers should be able to raid a gem box.
Just attacked a village with a gem box present. My attackers walked right by an obvious gem box on the way to a 100% 3 star victory and it occurred to me why not let attackers raid a gem box that they find?
Gem boxes could be given a high "hit point" value to make them a hard treasure chest to break into.
Maybe not allow taking all the gems, but this would be a way for people to get gems in an attack. This will also give an incentive to clear out your gem boxes in your own village. This also provides additional incentive to check your town daily.
Last, gem boxes could vary the content between 25 and 100 gems. Attackers could take up to 20%.
Why have raiding parties looking for glory, fame, gold, elixir, DE just walk by a treasure chest at the end of a rainbow?!
A gem box is not the same as someone's storage or purchased loot
The idea is about the randomly dropped gem box with the rainbow. This idea is not about taking someone's purchased or accumulated gems. Remember, there is no gem storage facility.
I don't think dropping down to 200 trophies will result in finding more gem boxes. Even if there are more abandoned towns at a low level only getting 5 gems in an attack (where the rare gem box is found) will not encourage this behavior.