Most likely the coding for this would be prohibitive, but it never hurts to ask:
It would be very nice to be able to select a group of objects in the Planning window and slide them about en masse. The simplest way might be a selection rectangle that slides anything it encompasses. The most elegant way might be to be able to shift-click the individual items to add them to the group.
Why do this? Well, for instance, an inlaid patio is made up of a couple dozen tile pieces. Once it's designed, what if you realize it would be much better two feet to the south, or on the other end of the lot where it would fit after all despite your graph paper predictions? What if you carefully lay out a fountain atop tile, /just/ covering the dirt gaps, only to find out you haven't left room for a dragon to walk between it and the gazebo? Or you've got a lovely bower arrangement of trees, but darn it, you need to rotate it so the entrance is more hidden?
Whatever the reason, there are many lovely arrangements out there composed of many small units that might benefit from better placement once one sees them in place. Yet the work in sliding and lining up ALL the planned pieces is so daunting ...
-Levity Merrel, Crai Aisling, Sans AoP by Aiya's pad ready for Phase III of renovations
(if there are no further transport errors during planning)