Wall selection/upgrading

I enjoy the select row for upgrading walls, but the issue is the corners would get upgrades twice making it difficult and individually go through each one upgrading. Maybe apply a touch drag select similar to placing walls while building them in editor mode? Just to allow easier selection and upgrading.

edit: also allows quicker upgrading if you can't afford a full row's upgrade fee.

The easy solution would be to remove the corner piece, breaking the solid line connection. Then upgrade that row, then put the corner piece back. Very tiny effort.