Swap button

The swap button: when tapping a building , there is a button (next to upgrade etc.) that lets you swap the towers place with another building. For example if you wanted to move your Archer Tower to where a cannon currently is, you tap the archer tower, hit the swap button then tap the cannon. (Note, there will be an error if one of the swapped buildings is too big.)

It would help, but how often will you need it? Also, it is possible but I dont thinks it's worth the effort. I do think the wall feature worked great so you never know.