Experts and BHG readers answer.
How do I create an accent wall in my bathroom?
Your home sounds really neat and the textured wall you are describing sounds pretty cool. I imagine you can accomplish this a few ways. Take a look at some other cementious materials for your inside wall finish. (I am thinking of Nichiha but there are others.) They have some pre-finished panels which would give you the textured look without being as rough as the plank outside.
You should also go to a local tile shop and see what sort of textures you can create from what they have available. Tile is no longer the 4x4 white squares we grew up with. We have done installations that look like cut stone, inlaid wood planks, beach pebbles and even more. This might give you the best blend of texture without being “too rough”.