A little Minecraftonian help please

I am currently making a game like minecraft where you can build things out of blocks. Everything was going fine until I had this thought:

I wanted to added be able to add armor to the outside of blocks. In minecraft 1 block = 1m cubed. In my game 1 block = 1m cubed, however I want to add armor at .5m intervals. This could be solved by having a block that is only half full of armor.

 |A |   blank space = air
 |A |   A = armor

However, I want to be able to have:
block, .5 armor, block.
With no space between the .5 armor and the next block.

To solve this problem would I have to reset the scale of my world, where the standard cube is actually 4 sub-blocks in one?

The planned average structures size is about 500 x 500 x 500

While making .5 blocks it be a bit of a performance hit seeing it would then be 1000x1000x1000 blocks in the same space.

There blocks are used in the blue print design phase so if anyone has some great advice on how to combine the blocks at render it would be greatly appreciated or other advice on how to solve my block armor problem would be great!

what minecraft do is that it multiply the number of possible block. You can do the same.

if you want to have: block - armor - block

then invent a new blok that is a “block halfarmor”

then if an armor is put between two block, you can just transform that “block - block” into “block halfarmor - halfarmor block” ( with oriented block)

it will be transparent for the user.