First, I think RW has an amazing building system. The building tools system allows a great range of style building, from castles to Roman architecture to cabins. Window frames that allow the glass to scale itself to fit is awesome. There are many touches like these that make me excited to see what is coming up next. I love the game world. The choice of biospheres for the styles are amazing and beautiful too and so important to the overall setting of buildings.
Some things I'd like to see relating to building:
The grid system is very good. However I 'd like to see a way to scale what we are building besides using the blocks by dragging them along the length of walls ect.
Ability to pick up ALL wood from the ground, same as we can pick up blocks of stone. I waste so much wood (I know it's my fault, but still....)
On the Block Bench there are big blocks of wood listed under the planks. One in particular is a nice brown rough wood that I use on appropriate floors. But, they have to be fit into block sized areas because they are not 'real planks'. I'd like to see these wood blocks as actual planks on the Saw Bench also.
Shingles. A panel of shingle patterns that we could size to fit. Or place singly if we had to.
Straw or Hay roofing for peasant style huts.
Ability to make angle cut beams or boards for supports.
Spheres in game. And the ability to size them.
Basic wood and stone blocks about a quarter the size of the ones we have. Not sure if that's possible though.
Arches in various sizes: longer, and or wider
More metallic surfaces to build with, besides copper. Like silver and gold.
Ropes in both straight sections and small wide half coils, and full coils
Chains in both straight sections and small wide half coils.
Ability to make cloth into objects like robes and tapestries and carpets.
Ability to make flags and mount on staff.
Area delete. Like the blueprint command but once the area is highlighted, hit 'delete' and all gone [one pick at a time on a castle wall is a very long job].
Negative building: Make a large sphere and then placing a smaller sphere inside it, hit 'remove' and the center disappears. Now have a large hollow sphere. (we did it with voxels in LM. Not sure if pixels allow it?) Fun though.
All I can think of at the moment.