There are many times that I'd like to make an angle on plextanium (glass) meet perfectly with hull. It's just not worth the cost of block IDs. Maybe it would be possible to have a building option that wouldn't take up extra block IDs, where the builder opts for the surrounding blocks to "fill in" the extra space with like-visuals. Since I usually use all-like (same color) blocks all around angled glass for angled windows, the surrounding hull would simply "bleed" into the extra space left by the angled glass, leaving no void.
Imagine this mechanic: You select one block of the surrounding hull as if you were picking a weapon computer ("C"), then pick the angled block as a subordinate ("V"). Then the game engine knows to "complete" the cube of the subordinate block with the surrounding hull, so that the surrounding hull would basically be copied to the subordinate's location, and then part of that copy would be overwritten with the subordinate block.
Edit: A visual might help.
Current build:
AAAA---B
AAAA--BB
AAAA-BBB
AAAABBBB
What happens when using the "completion" mechanic:
Rendering step A:
AAAAAAAA
AAAAAAAA
AAAAAAAA
AAAAAAAA
Rendering step B:
AAAAAAAB
AAAAAABB
AAAAABBB
AAAABBBB
Aside from using rendering tricks, I imagine it might be possible to use opposing block types to fill in the gap within the same cubic area when using the same master-slave block relationship.
Opposing Blocks:
Wedge: Wedge
Corner: Wedge (there really isn't an exact opposing shape for Corner in the game (yet), so wedge would be the closest candidate)
Tetra: Penta
Penta: Tetra
The game engine would simply fill in the extra "space" left over by the angled block with an opposing shape of the selected block.
From an inventory point of view, if this opposing-piece-fill option were implemented, it would check for and use up the appropriate block in your inventory. If the piece that fills in the space is not available, you don't get to fill in that space). I think it would be fair and acceptable to simply lose the opposing block when salvaging or rebuilding that particular block. It may seem difficult to lose that corner piece to oblivion. However, I think it's good to try to keep the game as streamlined as possible, which includes not placing some sort of weird double-block flags in these special block locations.