Ability to move obstacles
I for one would love to be able to keep certain obstacles, but simply be able to move them when they interfere with a new base layout.
It could simply be made that it costs just as much to move an obstacle as it does to remove it, and once its been moved, you can pay again to either move or remove it. That should keep the spirit of obstacles in operation while giving the users the ability to keep maybe a gem box (for those that love to make a base with the gem box as the center) or for xmas trees and other seasonal items that they simply want to keep around to show off.
EDIT: as to avoid people trying to farm gems and xp from constantly moving the same obstacle, xp and gems will only be granted on obstacle removal, and simply moving them gives nothing.