Working on trying to recreate some buildings has lead me to a real conundrum. I can design very elaborate shapes with say, Framed Glass or Ashlar, but I can't actually combine the two shapes without a block of separation between them. Many of the T5 blocks already share similar block designs; it would be fantastic to have full cubes that are made of half of one block material type, and half of another to allow you to seamlessly blend borders visually on your builds.

An alternative could also be the game engine simply recognizing negative space that another block can fill in, but I suspect that would require fundamental changes to how buildings works and thus mixed block types would be much easier to implement.