Clash of clans already has various achievements for upgrading, and unlocking new buildings and troops. Since walls cost so much and take a while to level up, why not reward us with some gems for upgrading them? We already get rewards for destroying walls, stealing gold, etc. I think it's only fair to include some sort of 'wall upgrade' related achievement since it's a key factor in the game.
I think level 5 walls are reasonably obtainable after a few weeks of playing and I think 10 or 20 gems would be a nice reward, especially for someone going after their 3rd builder. Level 7 walls are much harder and would probably be obtainable after several more weeks of playing. Upgrading all the walls from level 5 to 7 would cost roughly 50 million gold if my math is in the ballpark(for town hall 7), which is a solid chunk of gold. I think a reward around 100 gems would be fair for that. Then come the level 9 walls which I haven't even gotten to yet. I'm not really sure how difficult getting level 9 walls are, but I think 500 gems could be reasonable for that? Higher level or more experienced players could give you a better idea on that. Regardless it'd take well over 100 million gold to get there and it's not like players are going to quickly accomplish that.
A couple people have also made suggestions to set the rewards after you upgrade every 'n' number of walls to level 'X' as opposed to upgrading ALL walls to level 'X', which was implied in the title. For instance a tier two achievement could be 'upgrade 150 walls to level 7'. Using this method, a player rushing their town hall wouldn't have to upgrade any more walls for the achievement.
The following is what I think would be fair for each star of the 3-star achievement.
1st star- upgrade 100 walls to level 5--------------- reward 10 gems
2nd star- upgrade 150 walls to level 7-------------- reward 100 gems
3rd star- upgrade 200 walls to level 9--------------- reward 500 gems
Overall, walls are a significant part of the game, and as players we spend a lot of time farming just to level up a few segments of wall at time. I think tying in some sort of reward would be nice and fitting since it's not only time, but also gold consuming!
Hopefully this idea could get some consideration if it hasn't been already suggested and you guys can feel free to add some more feedback.
Thanks








